We have been seeing symptoms of this problem for a while now... water level fluctuating and getting high. I'm not sure what the real problem is, IE clogging etc of the overflows, but on one of my last visits, I had dialed the return back a bit and that seemed to steady the water level. If that has been re-opened fully, that is probably partially the reason for the recent overflows. Also, I think our overflows need to be lowered, so that the air intake is below the tank rim. Then when the water level gets too high, the air intake will get filled with water and creates a siphon, stopping potential overflows. Neither of the above are fixes for the root problem however.
In any case, overflowing water cant be good, as it's removing salt and we are replacing it with kalk, which can also cause more issues. I think the return should get dialed back furhter if necessary until we can address the issue.