You can't trade with villagers on slimeblocks

I thought I was going to trade with a villager

It was on slime blocks, when you activate the villager the trading screen flickers and you can't trade. When I pushed him off the slimeblocks, I could trade normally.

Steps to Reproduce:
1: Spawn or push a villager on to a slime block
2: Try to trade with villager [Doesn't Work]