Given that it's a message that flashes across the screen for a fraction of a second....

And also the fact that group summon is a collaboration effort and I can't very well take time out of it to collect such thing for you at expense of not helping out in it...

No, I can't.

But I WILL tell you how to reproduce this bug.

Step 1: schedule a group summon

Step 2: Enter the group summon with your character along with that of a group mate

Step 3: Try to invite said group mate from step 2.

You can do this in stage 1 of the group summon, it's the same throughout. You will be told that you can't form a team.

On the other hand, team is allowed, proven by:
Step 1: schedule a group summon

Step 2: Before/during the group summon, form a team outside the summon interface (note this can be inside or outside group base)

Step 3: enter the summon area as a team (leader can do this)

Ergo, team is allowed, therefore not allowing to team up in summon interface shouldn't be intended as it's self-contradicting.

Imho it's better to make groups BEFORE entering the summon. That way nothing can go wrong. It happens too often that you can't make groups anymore once inside Summon.

My apologies for the long wait.

I'm not responsible for the schedule of events in my group, I'm just a member.

That being said, lately I was unable to participate in the events. I will let you know the answer as soon as I will be able to.

I didnt notice Qolem asked for a screenshot...

I ask ppl on my server to take screenshot of them not being able to invite ppl to team up in Summon Fight (cuz I don't know how to do it on tablet lol!)

Th person invited was standing right next to him.

i dont know if this has been mentioned, but in the future, the summon will become unkillable and you will be best off forming teams for maximum rewards