No, there were no summons involved. Also, sorry but I'm not sure I understand what you're saying to try.
We end up in combat (unavoidable based on where we are) as soon as we enter the zone but then one of the characters gets "dropped" from the icon list at the top showing who gets to move in what order for the fight. Fight proceeds until it gets to where that character would've been in the sequence, then stops. That character -- which seems to be out-of-the-fight -- can take a few actions as if they were in combat (even though their UI looks like out-of-combat mode), and then anything else they do has no effect. They can continue to walk around anyplace they want, they can click on abilities, but using them has no effect, and nobody else gets a combat turn. None of the other characters can do anything at that point because it's "not their turn" in combat.
Fleeing combat will get the other character(s) out of combat and everything seems fine until you bring the glitched character anywhere near the rest of the party, at which time they all (all but the glitched character) go back into combat mode, even though there may not be any mobs nearby.
