For some reason I can no longer add brush adjustments to one of my photos.
As soon as I add one more brush stroke the photo resets to its original undeveloped status.
Going back to the history one step saves my work but otherwise it's impossible to continue working on it.
I have no idea of why this is happening.
Does it mean I reached the max adjustments per photo? (does it even exist a limit)
I don't have an answer, although as far as I know, there is no limit to the number of adjustments you can perform on an image.
You need to understand you are not talking to Adobe Support here in this forum.