Someone else suggested this already, I repeat: a good software dev would be able to write up a bug report for this showing how to repeat it with exact steps and maybe Network/HTML trace from the debug console of any modern browser. It would be easy enough to turn that on persistently until the bug happened again. Then submit the relevant portion of the log (with passwords scrubbed if present) to pmdev.

I have no idea if this is a real bug or just user/user-env error and neither do you. Since it’s never happened to me and I’ve never seen anyone else mention it, I lean toward the latter.