I would say you are having 2 problems then.
air flow and cooling capacity.
you are on the ragged edge of just enough cooling capacity with the rad wide open.
your 10 sec with no air flow brought the temp up but you don't have enough extra capacity to shed the extra heat built up in the coolant back to normal running temps.
or maybe just enough to get it back down to 188 from 190.

I bet that if you ran it hard, without the fans the temp would climb too then even with the rad wide open like it is.

you can test that too if you want to be sure.
drop it into low and run around and see if that brings up the temp above your 183.
Depending on your gearing, you might be reving pretty high to keep it over 40. That will tell you something too.

If it stays at 183, I would be surprised, but it would be another data point.