When doing my BQs:

Oh No! You can only attach 8 weapons!

Of course I HAVE only 8 weapons attached. Refreshing the page won't work, need to go back and restart the battle. Happens with nearly every opponent.

I made a thread about it a while ago. It appears that the preselection settings is sometimes slow to load, and if you enter a battle without it fully loaded, then you will get this message. The preselection data is pulled out of local storage on your device, but there may be other factors that cause it to be delayed by a few seconds and increase the chance of this happening.

Thanks!

Please see You Can Only Select Eight Weapons