Yeah, bench set up being off a bit could indeed throw you off, like you noticed. And I have a lot more disappointing chest days than I do good ones, but as long as the last good one was better than the good one before, its all in the right direction.
I know for me bench is the hardest mentally to constantly gain on. Squats and deads I'm not afraid to throw on another ten pounds and bust out one, maybe two more reps. I'll sure as hell feel it the next few days, tho
Last time I tried anything I could bench 325 x2, after working 275 8x3. Currently ( I say that but haven't done jack for a couple mos now) I'm back around 255 x5-ish, and thats about it. But within a week or two I could prolly do 330 x2 or 310 ish x 3 after a regular 3x8 routine.
Its all in your head!!