Which OS are you using? I've been experiencing a similar issue on Windows 10 but a quick work-around is to just save the Wattman settings as an XML file and load it up if the defaults are set again. I'm not sure why it does this but I think it could be a bug with Radeon Software and Windows.
I have encountered the same problem.
I suggest you save the data. And reapply them after "restore default"
Restoring default settings usually occurs after a system power outage / Windows update / drive hang or other problem
I tried to solve it... I have not found a solution at the moment. According to my observations, I think this has nothing to do with "power limitation."
But I still recommend that you report this to AMD.
I've reported the issue before but nothing has come of it yet. I have also yet to identify any sort of pattern in the defaults being restored but it seems totally random for me. Sometimes it's working correctly for days at a time and other times it seems like the defaults are set on each startup; with alternating days here and there too. It's been wonky like that for awhile, for lack of better words.