I'm seeing this issue repeatedly in my single player world. It seems to happen when the dimension the miner is in is unloaded e.g. I took a trip to the Nether and End and the miner disappeared from my overworld base both times. I can do more testing if necessary, just let me know what information you need. This has happened 2 or 3 times in the past couple days so I shouldn't have trouble reproducing it.

Experiencing same behavior. Also, #4114

Logs? Reproduced in mek only environment? Versions?

Same issue in MP. Not fun.

Duplicate of #3718