I also have such problem with a rezzer under Experience. But not all time, some days it works, some days not. The rezzer is deeded to land group but the land is not set to "group can rez".
Another rezzer i have on same land but not compiled for experience (only the object it rezzes is) never fails.
When group can rez on the land (wholegroup, not just a role) rezzer just need t be set to group and not deeded.