@Johni0702 here are the logs that I got from startup to crash while rendering:

21:30:06.255
Starting C:\Users\karee\AppData\Roaming.minecraft\ffmpeg\bin\ffmpeg.exe with args: -y -f rawvideo -pix_fmt bgra -s 1920x1080 -r 60 -i - -an -c:v libx264 -preset ultrafast -pix_fmt yuv420p "test2.mp4"
21:30:08.580
---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 4/23/20 9:30 PM
Description: Rendering video

java.lang.RuntimeException: GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT
at net.minecraft.class_276.method_1239(class_276.java:146)
at net.minecraft.class_276.method_1231(class_276.java:123)
at net.minecraft.class_276.method_22596(class_276.java:65)
at net.minecraft.class_276.method_1234(class_276.java:54)
at com.replaymod.render.rendering.VideoRenderer.drawGui(VideoRenderer.java:437)
at com.replaymod.render.rendering.VideoRenderer.updateForNextFrame(VideoRenderer.java:216)
at com.replaymod.render.capturer.SimplePboOpenGlFrameCapturer.process(SimplePboOpenGlFrameCapturer.java:55)
at com.replaymod.render.capturer.SimplePboOpenGlFrameCapturer.process(SimplePboOpenGlFrameCapturer.java:13)
at com.replaymod.render.rendering.Pipeline.run(Pipeline.java:71)
at com.replaymod.render.rendering.VideoRenderer.renderVideo(VideoRenderer.java:175)
at com.replaymod.render.gui.GuiRenderSettings$8.run(GuiRenderSettings.java:239)
at com.replaymod.core.ReplayMod.lambda$runLater$5(ReplayMod.java:493)
at com.replaymod.core.ReplayMod$$Lambda$1641/371271246.run(Unknown Source)
at net.minecraft.class_1255.method_18859(class_1255.java:144)
at net.minecraft.class_4093.method_18859(class_4093.java:23)
at net.minecraft.class_1255.method_16075(class_1255.java:118)
at net.minecraft.class_1255.method_5383(class_1255.java:103)
at com.replaymod.core.ReplayMod$ReplayModExecutor.method_5383(ReplayMod.java:472)
at com.replaymod.replay.InputReplayTimer.method_1658(InputReplayTimer.java:72)
at net.minecraft.class_310.method_1523(class_310.java:953)
at net.minecraft.class_310.method_1514(class_310.java:619)
at net.minecraft.client.main.Main.main(Main.java:204)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:192)
at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:140)
at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:26)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- System Details --
Details:
Minecraft Version: 1.15.2
Minecraft Version ID: 1.15.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 839870240 bytes (800 MB) / 3019898880 bytes (2880 MB) up to 4294967296 bytes (4096 MB)
CPUs: 8
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx4G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Fabric Mods:
fabric: Fabric API 0.7.1+build.301-1.15
fabric-api-base: Fabric API Base 0.1.2+b7f9825d0c
fabric-biomes-v1: Fabric Biomes (v1) 0.1.5+3b05f68e0c
fabric-blockrenderlayer-v1: Fabric BlockRenderLayer Registration (v1) 1.1.4+c6a8ea890c
fabric-climbable-api-v1: Fabric Climbable API (v1) 1.0.0+e40501d40c
fabric-commands-v0: Fabric Commands (v0) 0.1.2+b7f9825d0c
fabric-containers-v0: Fabric Containers (v0) 0.1.3+b7f9825d0c
fabric-content-registries-v0: Fabric Content Registries (v0) 0.1.3+b7f9825d0c
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.1.2+b7f9825d0c
fabric-dimensions-v1: fabric-dimensions-v1 0.3.0+2ad156310c
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.3.0+fac69e320c
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.1.2+003643510c
fabric-item-groups-v0: Fabric Item Groups (v0) 0.1.6+ec40b2e10c
fabric-keybindings-v0: Fabric Key Bindings (v0) 0.1.1+dfdb52d60c
fabric-loot-tables-v1: Fabric Loot Tables (v1) 0.1.5+e08a73050c
fabric-mining-levels-v0: Fabric Mining Levels (v0) 0.1.2+ec951ea40c
fabric-models-v0: Fabric Models (v0) 0.1.0+dfdb52d60c
fabric-networking-blockentity-v0: Fabric Networking Block Entity (v0) 0.2.3+e08a73050c
fabric-networking-v0: Fabric Networking (v0) 0.1.7+003643510c
fabric-object-builders-v0: Fabric Object Builders (v0) 0.1.4+ec951ea40c
fabric-particles-v1: fabric-particles-v1 0.1.2+ad2f81bd0c
fabric-registry-sync-v0: Fabric Registry Sync (v0) 0.2.6+f3d8141b0c
fabric-renderer-api-v1: Fabric Renderer API (v1) 0.2.10+f08b61330c
fabric-renderer-indigo: Fabric Renderer - Indigo 0.2.23+9290e2ed0c
fabric-renderer-registries-v1: Fabric Renderer Registries (v1) 2.0.1+5a0f9a600c
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.1.3+b7f9825d0c
fabric-rendering-fluids-v1: Fabric Rendering Fluids (v1) 0.1.6+12515ed90c
fabric-rendering-v0: Fabric Rendering (v0) 1.1.0+534104900c
fabric-rendering-v1: Fabric Rendering (v1) 0.1.0+003643510c
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.1.10+06c939b30c
fabric-tag-extensions-v0: Fabric Tag Extensions (v0) 0.1.3+abd915800c
fabric-textures-v0: Fabric Textures (v0) 1.0.4+821cdba70c
fabric-tool-attribute-api-v1: Fabric Tool Attribute API (v1) 1.0.2+915c44630c
fabricloader: Fabric Loader 0.8.2+build.194
minecraft: Minecraft 1.15.2
replaymod: Replay Mod 1.15.2-2.3.0-b1
21:30:08.604
OpenGL debug message, id=1286, source=API, type=ERROR, severity=HIGH, message=Error has been generated. GL error GL_INVALID_FRAMEBUFFER_OPERATION in (null): (ID: 4012793211) framebuffer 4, "" is not complete
21:30:08.604
OpenGL debug message, id=1286, source=API, type=ERROR, severity=HIGH, message=Error has been generated. GL error GL_INVALID_FRAMEBUFFER_OPERATION in (null): (ID: 173538523) Generic error

Originally posted by @kareemAlramlawi in #135 (comment)

OK, Minecraft crashed on me here is the rest:
21:36:35.653
Starting C:\Users\karee\AppData\Roaming.minecraft\ffmpeg\bin\ffmpeg.exe with args: -y -f rawvideo -pix_fmt bgra -s 1920x1080 -r 60 -i - -an -c:v libx264 -preset ultrafast -pix_fmt yuv420p "test2.mp4"
21:43:33.459
21:43:33.459
Process crashed with exit code -805306369
note: The first time I clicked "render", render window appeared until it froze at Random frame then crashed.
This one I tried opening sniping and sketch window, then the crash log appeared.
anything you want :)

just in case.

Also, this appeared after I clicked a few times while RM renderer was frozen

all of these were fullscreened except the launcher and the output log.

Also after I closed the crash log from the mod, I clicked "render" then this started flashing for few times until it fully showed(and the background was RM renderer)

Originally posted by @kareemAlramlawi in #135 (comment)

The GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT crash is the same as #140, even if you never minimized the window.
The freezes are likely the same as #156 (unrelated to optifine).
Both should be fixed in the next release.

thank you very much for taking care of this common bug.