actually the last few tournaments on the list with property "in progress" are not.

e.g. Tournament 1942 looks finished by a long time, but is listed as "in progress".

Could it be that it has to do with bannings?

Actually some of the tournaments in progress have a tick besides the "in progress" sign. (Website) but it doesn't seem to be connected to the state of the tournament.

All five of the tournaments listed as Mega Quartets I on the final (24th) page of the "in progress" list have been completed and say "group complete" on the detailed page. Most have no banned people and there are no unfinished games. Coding bug maybe?