4rgh is my friend and were in a party together (not quest party). Everytime the server restarts he loses the ability to do anything. The only way I have found to fix it is to kick and reinvite him. This causes him to lose his inventory each time as he cannnot drop items or access chests. I have to leave for a few hours. 4rgh has full rights to anything on the island.
The ability to access anything or break blocks. Essentially it's like I never invited him but he still shows up when I check island perms.
As I said in the OP that's the only way he can build until the next restart. This happens every time to him. He has lost several rewards and projects he was working on because he comes back on and cant do anything. When I kick him he loses everything in his inventory. This also means that I have to be on in order for him to play. I have kicked and re-invited him 3 or 4 times already and the same issue persists.