spams this in the logs around 30 times right before making a backup
[01:00:08] [FTB Backups backup thread 0/WARN]: Failed to render chunk (10, 25) section 19. This is very likely because your chunk is corrupt. If possible, please verify it manually before sending a bug report. java.lang.NullPointerException: Cannot invoke "net.creeperhost.ftbbackups.de.piegames.nbt.CompoundMap.get(Object)" because "section" is null at net.creeperhost.ftbbackups.de.piegames.blockmap.renderer.ChunkRenderer_1_18.renderSection(ChunkRenderer_1_18.java:297) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.de.piegames.blockmap.renderer.ChunkRenderer_1_18.renderChunk(ChunkRenderer_1_18.java:191) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.de.piegames.blockmap.renderer.RegionRenderer.renderRaw(RegionRenderer.java:149) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.de.piegames.blockmap.renderer.RegionRenderer.render(RegionRenderer.java:61) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.de.piegames.blockmap.world.RegionFolder$WorldRegionFolder.render(RegionFolder.java:179) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.de.piegames.blockmap.world.RegionFolder$CachedRegionFolder.render(RegionFolder.java:467) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.BackupHandler.createPreview(BackupHandler.java:150) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at net.creeperhost.ftbbackups.BackupHandler.lambda$createBackup$4(BackupHandler.java:262) ~[ftbbackups2-fabric-1.18.2-1.0.18.jar:?] at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) [?:?] at java.lang.Thread.run(Thread.java:833) [?:?]
i flew to the chunk 10, 25 (f3 showed 10, 25)

i hadnt even loaded that chunk when the backup happened
modlist:
mods.txt

Fixed in 1.0.19