I've had this same problem both in and out of combat. It is not only limited to my party as I have also seen the AI falling victim to the same issue. Locations that I have seen this happen have mostly been in the Goblin Guardpost just after the Goblin Bridge, the Exterior of the Selune Temple and the interior of the Selune Temple.
I have had to abandon at least one game where a character ended up inside the terrain of the Selunite Temple and I could do nothing to get the character out.
