Was not able to sync my wallet properly around 2 weeks ago (5 weeks behind). Eventually managed to sync with 1 active user yesterday, phew!!
Tried to upgrade to latest dash core wallet software, but told 'fatal error' had occurred.
Any advice please?
As I have already suggested you, the removal of the appdata folder except wallet.dat and backups folder and starting the v14.0.2 should solve your issue.
It didn't solve the problem, but thanks anyway!
PS: You know this question is from 15 days ago right?
Of course I am, haven't checked this side for a while but decided to answer anyway :)
We keep your issue on support desk though.