Minecraft Version

1.15.2

Forge Version

31.2.36

Mod Version

pneumaticcraft-repressurized-1.15.2-1.5.1-81

Describe your problem, including steps to reproduce it

A couple of villagers have closed their trades, trading other items do not seem to make the villager reopen their trades or regain their health. The villagers are masters and I think it works up to this level.

Is this the correct behaviour?

To be honest, I'm not sure. The official wiki suggests that they can replenish their stocks (a couple of times per minecraft day) by working more at their job site, which is a Charging Station for pneumatic mechanics. Do your villagers have access to Charging Stations?

Yes placing a charging station near the PneumaticCraft villager opened his trades again.

What happened is that I placed a charging station on the outside wall of an unused house and a villager was converted to a PneumaticCraft villager and then for some reason he wandered off and a new villager became a PneumaticCraft villager. As soon as a second charging station was placed by the first villager the second villager appeared by the first villager. Now I placed down a third charging station by the second one. Let's see what happens.

They don't regain health with the trades, maybe they need a house too.