Unable to switch characters now?

I'm also having this problem, but on the PC.

DItto on PC version, it happened when trying to energize the rocks and again during battle trying to close a rift. If you save and reload you can switch characters again but that's pretty annoying. 

I have a ps4, up and down arrows are not working for me at all. I can't switch characters! Majorly furstrating.

Yep, Same here. PC version with Xbox 360 controller. I restart the game and it works for a few minutes before it cuts out again.

I had the same issue in the Hinterlands. I walked through a cave into a dragons realm, where the dragon summarily pummelled by team, killing all but Cass. I ran back to the cave, which allowed my team to revive, but my main character was stuck out a little further and got smoked two more times with fire balls.

When everyone finally came together, I couldn't change characters. I was stuck on Cass. I had to reload to fix it.

I had the same problem with the hinterlands cave... everything worked fine until then though, now I cannot switch out of the main character.  Playing on PC

This has happened to me a couple times, and the only way I can fix it is by saving and then loading that save file.