from what i've gathered the repro steps are:
closed forest
go to deku tree
leave deku tree
get blocked by mido on the way back in to KF

haven't tried to reproduce yet

spoiler: 27090.json.txt

from edgebug on discord:

He says something about how he can't believe I'm Saria's favorite and the Great Deku Tree's favorite. Blocks my path at the Deku Tree entrance just like he does going the other way if you don't have sword and shield. It's bizarre

then after save/resetting, mido is blocking the way in to the deku tree, even with sword and shield