Since this bug might affect and confuses new users, I thought I report it:
Today I am playing on a borrowed machine with Firefox and Windows10. I logged into my account, and whichever game I selected, the minimap did not load on the first attempt. Hitting F5 fixed the problem in all cases, but that is because I know how the minimap should look like. A newbie might simply find the minimap confusing? Maybe this is due to my account having wrong assumptions about the cache, so I might not affect new users?