@Derelict:
I also saw a quirk in a DGS-1210-10P. Accessing the web gui same-subnet fails to load properly/consistently. Accessing it from another subnet so the traffic is out the management default gateway works fine. Weird.
I experienced somewhat the same, configuring an 1100-08 yesterday.
After moving the mgmt vlan to the "final" vlan , i got a "White screen" , even after several refreshes etc. (Using firefox)
No hangs or errors , so the 1100-08 was answering on http.
I didn't want to shutdown FF , so just opened a Chromium (Linux Chrome) , and entered the samme ip that gave white screen in FF.
Everything was ok in Chromium.
After (saving the new mgmt vlan change to flashcfg) , and a a reload of the 1100-08 … FF was ok too ???
/Bingo