What was Ash’s rank when he beat the Sinnoh Bug Queen? Was it somewhere from 750-840?
That would be pretty harsh to drop him so low after all the wins he’s managed.
According to Bulbapedia, Ash's current rank after beating Koromi is 890.
We have not yet seen how much your rank drops by when you lose (they've been careful not to show it so far), so it's possible for Ash to drop over 110 and drop back down to Normal Class.