Completed Spartan Ops solo legendary but no ach

Hi, hoping this is a solvable problem as id rather not have to replay all 50 levels. But every level has 100% been done solo legendary by me but the achievement tracker hasnt moved up from 49 even though i have redone about 8 of the levels to no avail.
Has anyone else had this problem?
I wouldnt mind replaying them all if spartan ops was fun To play lol.
Any help would be much appreciated.

Some missions don’t count as done go through and check if any aren’t marked as completed, I had a friend with this problem too and that worked

Thanks for the reply, every level has the legendary sign completed though so sounds like its glitched on me sadly.