I don't have a concrete STR but hopefully the screenshot gives some hints.
I've seen this a few times where the Changes panel shows every keystroke I've entered. I believe the initial value I entered was
grid-template-rows: 1fr 1fr. When I tried to turn that into
repeat(2, 1fr) things started to go haywire.
(Interestingly I never entered the
\ escape characters. DevTools decided to enter those for me and I had to delete them. Not sure why. Also, when I entered the extra closing
) after adding minmax, DevTools swallowed it because the next character was
\ so I needed to enter it twice.)
(And yet another totally unrelated observation, the property would be marked as invalid when I had
minmax(1fr, auto) since apparently that's not valid. It would be nice if DevTools could tell me why it's not valid.)