Armorer villager cant fill up the experience bar to advance to the next trading level. There are 2 trades available, but the trades get disabled before he can reach the next trading level.

Steps to reproduce:

1. Find a village with an Armorer (in my case snowy village)
2. Open trading menu
3. Max out all possible trades (in my case iron leggings and iron chestplate)

If this is an intended feature (as in the trades may reopen again later) then the feature is inconsistent as this does not happen with other professions that I have encountered so far, as they can reach the next level and unlock new trades before all trades get disabled.