Probably not the right place but Ill put it here as MIUI is my current ROM.
I have just started getting lots of FCs on my calendar sync.
As per many google searches, I have so far tried clearing web mails, google app caches, dalvik cache, and installed previous nandroids, miui version 30 as well as an "apps.rar" pack from the android forums - all with no success.
I sync contacts and mail ok - it just fails on calendar. There is some references in google links to clear the "Calendar sync" cache - i do'nt seem to have that file.