This bug has actually been fixed and is back in 1.15.2!
I know this bug has actually been fixed, but it is still there / back. When I recently placed a lectern, it was accepted directly by two different villagers. The same thing has already happened with two fletchers and that in several worlds. This bug is very annoying if you want to build a large villager exchange system. Please fix the bug as soon as possible, especially since it has already been fixed.
Duplicate of MC-150806