I have also used newest version to modify programming, and do FW updates on quite a few different models of APX, Never an issue until the other day.
Was working on some talkgroup changes on a very large and advanced codeplug and the invalid fields error showed up along with Please Contact Motorola Support.
The usual method of View invalid fields showed nothing wrong. Worked that issue for an hour up to and including restore previous version of CP from the shared drive, same issue happened.
Worked around it with a copy from a week prior, two days later made a change to that CP, and when trying to write to radio same issue happened, Invalid fields (5), Please contact Motorola support.
After speaking to them and creating a case I was made aware of the KB article I referenced above, which they said is an internal KB article and told I could "send them the codeplug for "repair", or wait until the new version is released that resolves the invalid code."
Hope that explains it better. It only happened to three codeplugs so far. They were large, maybe the amount of systems or the size is the underlying trigger?
Only went to newest release of CPS and FW for the Talk Permit Tone which was needed for a special setup. Normally I stay one release behind.