Did you test it again after switching back to WHC?
If it works now then this is a common/minor bug, you have to either switch classes or switch the weapon off and on again. If you reroll the trait of a weapon while it is equipped it will remain the trait you started out with, so if you had conservative shooter on it before rerolling and rerolled to scrounger, you wil not get ammo on crits but you will get your ammo back on headshots. Maybe rephrasing your bug report to smth akin to ‘have to switch weapon before it applies rerolled trait’ could work.
It is a rather minor bug though and with it only not working correctly in the keep but working in missions it may not be high on their to-do list, which is quite large at this moment.