polarbreeze1,
Thank you so much!
I've had this problem for over a year (MBP 13" Late 2012 running 10.11.6) and have gone through so-so many calls to Apple support . Have tried everything from deleting "Library/Application Support/iCloud/Accounts" and all keychains, system updates (but within El Capitain - as I could not upgrade to Sierra due to being locked out of the App Store... and also compatibility issues with some apps I run for my work), multiple SMC & PRAM resets, genius bar visits, loads of library file deletes, uninstalled a lot of apps, paid for new IO board & all sorts of diagnostics in multiple chat and phone sessions with Apple support staff.
One level one service person even insisted that I reseat my RAM, which is not possible with my MBP, they even sent me a how-to after I pointed out that the RAM was soldered in.
Anyway, your solution worked first time - so thank you again.
Meanwhile, it's slightly annoying that Apple Support knew of this issue but failed to make that info available to their wider team for their troubleshooting.
If I could buy you a beer I would. Thanks again!