sadly an age old issue.
it just aint the fps themselves, rather a stutter depending on where you are on the map.
for example entry hall and second hangar sometimes stutter like crazy, despite the recording afterwards being alright and no severe frame drops counted either.
the moment you move a pixel past a certain threshold the issue is gone despite sometimes more enemy density then before.
could be a mesh or lighting issue depending on what effects are played there, i dunno
to some extend relay station entry acts the same
had them issues on a rtx4080 and 5080 so i doubt its a hardware performance issue .