Villagers do not recognize workstations when they are in a 1x1 space or have blocks directly above their heads. They also do not lose their job when the workstation is removed. These villagers have not been traded with.
How to Reproduce:
Put a villager in a 1x1x2 space then place a workstation within view of the villager. Doing so in any other configuration causes them to instantly change however when they are in a 1x1x2 space or have a block above their head they don't recognize the workstation.
Workstations worked in a 1x1 space in 1.14 however in the 1.14.1 pre-releases this is broken.
Does MC-151079 describe your issue?