Hello everyone,
I've been suffering this issue since last October, but the differentiating element is that I work as a Sys Admin at a school and the Apple IDs that get locked are Managed Apple IDs that some of the students use with Shared iPads.
So, in an environment of more than 70 shared devices and more than 350 Apple IDs using that devices, you can imagine how frustrating is to get locked from 5 to 10 Apple IDs every week.
However, I'm "glad" to see that maybe it's not an iPads or network bad configuration.
Of course, Apple is not being very helpful, and in all this time, all they can say is that "user is introducing invalid credentials too many times". But the truth is that I have seen Apple IDs getting locked when the users were in front of me with no iPad in their hands.
Needless to say, the problem, 6 months later, is still happening.