Steps to reproduce:

1. Set Automatic Recording to OFF
2. Join the server, let chunks around you to load
3. Start recording
4. Fly around to load new chunks
5. Stop recording

Expected behavior:
When viewing replay, starting position around player should be loaded (chunks should be visible)

Unexpected behavior:
No chunks visible around starting player position, only new he loaded during recording.
https://i.imgur.com/9l4yv0E.png

P.S. Reloading chunks with F3 + A during recording does not help.

Info:

• Windows 10 x64
• Java 14 (OpenJDK)
• Replay Mod 2.3.0 b1 (1.15.2)

Other Mods:

• fabric-api-0.5.1+build.294-1.15
• optifabric-1.0.0-beta8
• OptiFine_1.15.2_HD_U_G1_pre13_MOD

Cannot reproduce:

I also don't see the player entity in your screenshot. Does it not render either?
Also, it seems like you're at about 50% of your replay, so right somewhere in the middle of 4. Fly around to load new chunks, so not seeing chunks at the place where the player spawned (i.e. where they no longer are) would be expected.

If this only happens with Automatic Recording disabled, then an easy way for me to reproduce it is for you to send me the replay and the similarly named replay from .minecraft/replay_recordings/raw/ (that's the full replay, without the automatic recording changes applied). That way the difference would be obvious (and I could also verify any potential fix).

Screenshot is a moment a bit later when I was flying and loaded few new chunks. At first position you see nothing loaded except your player, who moves around (but some move animations are broken due to no terrain).

I tried to reproduce that again with same version when I posted this (2.3.0-b1) (also with more mods including prev but seems this does not matter here) and got a bit another situation. Now some of the chunks are visible and some not in the recording. Demo:
https://youtu.be/qXa-jTxwXDU
And recordings (everything that were added to folder since it was empty):
replay_recordings.zip

I also reproduced this on new version (2.3.0):
https://youtu.be/OfyvrRNOwkg
replay_recordings_1.zip

There is new evidence that this is not resolved with ReplayMod-1.6.4-2.5.2; this is the raw recording from a single-player recording that used start/stop and was missing chunks:

Missing-Chunks-Raw-Recording.mcpr
(original name lost due to breiz.mp file transfer, renamed to .zip for github)

@LindaJuffermans This particular issue has definitely been fixed with 2.5.2 and cannot possibly happen on an vanilla server (or single player). Please always open a separate issue unless you are certain that it is the same bug.