I'm having a problem with farmers getting stuck in composters.

One wrinkle is my composters are embedded in slabs over water. Maybe the combination of slabs and water is confusing them.

I've had this village for about a week and had no problems.

Suddenly they were consistently getting stuck and spending the night in the composters. I started with three slabs and a composter over four blocks of water. The problem there was farm blocks were being destroyed by jumps. So I switched to having the composter surrounded by slabs. The water is the same. And I simply covered the dirt blocks with slabs. A composter surrounded by slabs is the configuration that has a problem.

Sometimes I will see farmers jump out if I am breaking slabs next to them. But, just as often, I have to complete the rescue and break the composter. 

The only other detail is this is a destination village. I do not live here. I travel here. And it is subject to chunk loading during the day and night. There are four composters and farmers. By chance, each composter is located in a different chunk. And where the four chunks meet is located in the middle of the overall farm field. I've seen three farmers be affected by this simultaneously. I have no reason to believe the fourth is immune. 

I've started using carpets to cover the composters. So, I hope to solve my problem with that.