Hi! Same here! Over 100 units got the same problem at a moment. Reboot doesn't help. Switch off/on doesn't help.
UPD: Firmware 3.5.25, 3.5.21 - no difference
UPD2: SET PLL method, suggested above, is not working
UPD3: Mining DASH on www2.coinmine.pl
Temperature values are the same via the WEB...