Only the best setups can sustain a full dive bomb and come back neutral, ie locking nut and well manufactured bridge
It could be coming from the wind on the peg, the nut, the bridge, the blade on the bridge ( not perfectly sharp) or something on the underside
I notice your guitar you has locking tuners, make sure you have as little wind on the turners as possible
One thing a lot of players have done (with non floyd setup-ups) over the years (you see this a lot in older clips of folk), is once they do a dive bomb and come back up, is to do a quick hit on the trembar
this motion in same cases releases enough tension to re-seat the strings (and variables) back in to equilibrium. some trems are notorious for this
Don't feel bad about it though, its a very common problem.
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Ill probably get flayed for this, however those sorts of bridges and without a locking nut where never designed to be dive bombed at the start of the set anyway. there are just too many many modes of failure that will kill your tunning
Also there is no guarantee when you last tuned everything was in equilibrium anyway, in which case it will never come back the same no matter what you try