The mod Single Train Unit (20.0.12) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event single_train_unit::on_pre_player_mined_item (ID 11)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__single_train_unit/scripts/entity.lua:523: in function 'handlerFunction'
single_train_unit/utility/events.lua:83: in function
<single_train_unit/utility/events.lua:78>

What other mods are on your game? A save with the specific versions and mod settings is best. If you can upload it somewhere.

It will likely be ages before I get to dig in to the issue though as busy IRL.