Farmers not restocking trades

I have been trading with 2 farmers and suddenly although they stand at the composters they didnt reset ( restock) trades. I went back several days in turn and still not reset.

One farmer is maxed and used the same composter and garden the whole time, the other had replaced one who had died. This was a desert village.

I tried breaking each composter one by one and putting in a different position, Still not restocked

Finally I broke both composters at same time while they were sleeping and put them down. again they sparkled and when the farmers returned to the composters they restocked.

I had seen this issue before caused by them swapping workstations but in this case the maxed farmer used the same one all the time and hadnt swapped ( composter was at the same garden plot the whole time ) and had continued trading after the other farmer died and was replaced and I had been trading regularly with them so not sure why they suddenly stopped restocking but the solution seemed to be breaking both composters at the same time to make them start restocking