yup apparently that was the whole issue here....
Thats because under ILR/ELC anything in creature slots will get destroyed when player logs into multiplayer server. Any decent skin system should account for that, but it is possible SSE was created before this feature was added into one of the 1.6* patches or maybe it has in readme written that you mustn't use ILR/ELC.
Also it is possible that the skin could not be equipped because of ILR restriction - IIRC skin is not treated any differently for player characters with regards to IRL so any permanent bonuses will impose a minimal level to equip.
Needless to say one project I don't want to mention fixes both issues, but I think you've heard about it already...