Playing on Win 10 via GeForceNow.
Before the big update patch, If I damaged FNIX bases, left and came back hours or days later, the things I destroyed (walls, spawners etc.) would still be gone.
After the patch I waited for the FNIX Ravinen base to fully upgrade, then I attacked it. I knocked out quite a few walls and several bot spawners. I left the vicinity to get some more ammo, when I returned a hour or two later everything was rebuilt. I attacked the base several more times, each time running out of ammo and having to leave to get more only to find the base completely rebuilt on return. On about my 4th try, when I left to get more ammo and returned a hour or so later, the damage from my 4th try was still there.
Also on side note once you destroy a FNIX base now, and use B to inspect the site and the screen shows you the option to claim the site, clicking on “claim the site” does nothing, you have to use E to use the option. You should be able to click on the option to claim the site.