I ported a Character over from a previous build because of a crash when trying to open the char in the latest build (maybe due to lifestyle, as I know now).
During karma-creation I purchased several skill groups (Athletics, Stealth, Electronics), which were later split because of buying specializations.
Applying career karma I tried to raise some skills above rating 6. I saved, closed the character and re-opened it and the skills were back at group level.
I could replicate it with a Prime Sum-to-ten build where I put Stealth at 6 and Athletics at 4 and raised individual skills in career mode.
It not only reduced skills back from above rating 6 but also a Computer rating 3 back to Electronics 1.