I'm on Lvl 14 right now and for the past 2 or 3 monster portals I can't seem to actually win because although all mobs are killed and I can't find any more, the timer does not reset for the next wave and only resets at sunrise. This however leads to me not getting the usual chunk of XP, which is quite annoying.

It worked just fine before, idk why the change now. Am I missing something? My game has some mods but again, it worked fine so far.
I haven't played to this level for a long time, is that normal at this stage?