I just beat the last spore portal and then the cutscene played and no boss base was spawned. I think this might be due to a portal still showing on the compass despite being destroyed. i tried loading an older save and beating the last horde of the spore portal again and nothing changed.

I am now soft-locked till whatever is going on is fixed because I can't fight the horde of the spore boss...

The image below was taken directly after destroying the nether portal.