As Enforcer said, Raze shouldn't be teleporting to the healing chamber, but running (where you have a chance to try to block his path and/or attack him).
If you stand in or near one healing chamber with your creature summoned and let the walking armours build up, that should prevent him from using that chamber, forcing him to run to the far one.
If you leave this until later, possibly one of the last things before heading to the Hall of Echoes, you may be able to do damage fast enough that Raze doesn't have a chance to teleport away.
Try emailing support@larian.com, with a description of the problem and maybe a link to this topic. With your save they should be able to fix the problem.
