I was wondering if somebody had an answer to my problem.
I have an A7III with a Godox Speedlite on it.
With the flash off my manual settings produce an underexposed shot that I can see as underexposed in the viewfinder.
With my flash on the viewfinder shows a much more properly exposed image
For months I had the AEL button set to 'Shot Result Preview' and when I would hold it down my viewfinder would show the underexposed shot preview
But lately when I press and hold it the viewfinder shows the same properly exposed image, but the frames per second drops to 5 or 10.
Basically 'Shot Result Preview' isn't working as intended.