"compliance incident" is the catchall for everything from a spelling error on a CPS (certification practice statement) or being one second late on revocation, all the way up to to key compromise.

it is almost always closer to the spelling mistake side than it is the key compromise side of the spectrum.

a peak at https://bugzilla.mozilla.org/buglist.cgi?product=CA%20Progra... will show that most compliance issues, to the general public, are quite mundane.