Finding which chunk or entity has the oversized NBT tag

Read the warning first

When the mod logs its warning instead of crashing, that log line is your starting point. Open the log for the session where the world loaded and locate the warning. It typically names the tag type and may include a path or context pointing at the offending data.

Narrow it down

1. Copy the save to a scratch location so you can inspect it without risk.

2. Open the copy in an NBT editor that can browse region files and level data.

3. Work from the clue in the log: if it mentions an entity, check entity data; if it mentions a block entity, check the chunk it lives in.

4. Compare suspicious entries against normal ones — the abnormal tag will be nested far deeper than anything around it.

5. Once found, note what created it: a specific machine, mob, or container is the usual culprit.

Practical tips

If the log does not localize the problem, load the world and watch for lag spikes or repeated warnings as you move between areas. The chunk that triggers fresh warnings is likely the one holding the bad tag. Remove or reset that block entity or entity, then re-check the log after a reload.