Okay, I was suspecting this now I can confirm it.
A pot just lost its unpaid status.
Tuukka, of my story thread, has long been staying at a month. Im doing the island challenge so he has chosen to get to this second island and stay in the village for the ice-bound months.
On an earlier visit to the trade house I picked up the pot (unpaid) and found it was too much to afford.
Week or so later Tukka has made a shelves to trade. The shelves are a custom BAC mod item. Being heavy I dragged them over. I wanted to see if the shelves would cover all or most of the cost of the iron pot. Picking up the pot and talking to a villager they don't acknowledge the pot as needing payment.
In my inventory the pot says (unpaid)
Dropping the pot the pot no longer says (unpaid)
I haven't given them payment!
I was pretty sure this free-pay had happened before with a bag of barley grains.
I think the common elements of the bug are:
- extended stay of weeks in a village
- making things in the village
- dropping and picking up my own things
- picking up an unpaid item
- dropping an unpaid item
- more crafting, dropping, picking up my own things
- picking it up as (unpaid)
- it has lost the (unpaid) flag
I have been doing my regular zip file saving so can send over game files at various stages.