Is your structure floor made up of foundations or ceilings? I've found that I still occasionally fall through ceilings when logged out. I have a base up on a cliff, with only four true foundations and all the rest ceilings and pillars, so I put a chair in the middle of the foundations and always log out sitting down. Haven't had the problem since.

Hi Crazy Hermit , the floor is foundation .. hmm I'll try sitting next time , it doesn't happen everytime but enough to become annoying , I've now made a cabinet to "undress" my items into before going to "Sleep" so I don't lose everything lol .. Thank you for the suggestion.