Stefan Andersson
Comments
I now switched to Peaceful mode temporarily. Then back to Normal mode. This opearation killed all the mobs in the caves so I could start clearing the caves with freshly spawned mobs. Problem solved and the bug is now not a major issue.
More details on this issue is that there are distinct boundaries within the mine between areas where the FPS is very low and normal. Moving across the boundary is fully repeatable, i.e the issue appeats always in the same area when moving around. One hypothesis offered by another player is accumulation of mobs. I have excavated the mine and deferred exploration of any caves found on the way. Does this way of working create too many, permanently spawned, zombies surrounding the cave? If this is the root cause, I would still consider it a bug. I can't clear the caves in a reasonable way with the low FPS.
Happened also to me with full netherite armor with feather falling 4 boots. Really annoying bug! Maybe this is somehow dependent on the specific armor configuration... V1.17.1.