When the hammer swings, such as when it's in the off hand while chiseling and you break the block by hand to move it to a better angle, the animation has it come directly towards the character's face/the player's camera, completely filling the screen on standard FOVs.
Especially since well lit environments will be lighter in color than most of the hammers, this creates a mild strobe effect as the screen switches from light to dark rapidly.
I have photosensitive headaches and it's more than enough to start setting one off if I don't close my eyes until I hear the block break (or switch it out of my hand and then switch to another hotbar slot, which gets annoying when doing a lot of chiseling). Given that, it's likely more than enough to set off some people's epilepsy.
Also on a realism standpoint, hammering like that is a really good way to take a hammer to the face lol. When I was metalsmithing studio monitor back in college that was one of the things I was told to look for and correct.
The head of the hammer should be going over the shoulder, so if you do lose grip you kind of throw it over your shoulder instead of breaking your own nose. Or it can be parallel to the plane of the face, which is more the traditional blacksmith swing where they're moving the hammer up and down more than side to side, but depending on the animation that could also trigger strobe sensitivities.
Thank you for all the work you've done, and the number of accessibility settings you've already implemented!