The FRE in an F3 controls the aperture/shutter speed/light value, so when it breaks it either renders the meter completely non functional, off by a large amount of f-stops, or 'jumpy'. I've got a very early F3 12xxxx serial that took a hit to the film rewind side and the FRE was replaced by Nikon back in 93 or so, it started out as jumpy and then got worse. That F3 also had the right side top plate replaced, the one with the serial number, so it went from very early production of 12xxxx to very late production of 19xxxx.
From my own experience of F3's (4 of them including an ultra tough P version) the FRE is probably the weakest part, but its reasonably protected on that side and you gotta really want to hurt the camera to crack it. Mine had a pretty serious toss on to concrete, and the impact to that corner by the film rewind knob was obvious as was damage to the rewind assembly, making rewinding by hand a squeaky and friction filled event. All credit to the F3 though, it continued to work in Manual at the marked speeds with the meter being jumpy for a few weeks until I could send it in to get fixed. I was a news photographer at the time and those types of damage stories were part of the job, I remain impressed with how tough that camera is.