on my side I've encountered another issue.
I use 7.0R2 and tried to upgrade to 7.0R3, => Failed
The system indicated that 7.0R3 is older than 7.0R2...
The time can vary depending on a few items. If you backup and then delete all logs (access, admin, event), it can help speed up the process sometimes.
I haven't heard of the issue of the newer release failing to upgrade the older rev. I'd open a case with JTAC to have that looked at if I were you.
finally it works perfectly.
I downloaded again the 70R3 and saw that my package file has a size which was approximately 210Mo ... whereas last week the one that I downloaded was 208Mo.
BTW, with the new one, the upgrade was done without any issue