The Hidden Forest

Frequently, after downing a vampire in Dreadspire I, instead of the normal behavior of the vampire falling at the spot of battle, it instead begins to "warp around" near the battle area, often going below ground level. This occurs for about 10 sec with the vampire returning near full strength. Ugly because it draws the attention of all pets, forcing the group to run after the warping vampire to kill it. After a few of these cycles, it will eventually fall "normally" at the battle site, allowing you to use the ear-ring to stake its heart. This phenomenon is happening roughly 50 percent of the time to me ... very annoying.
Anyone else seeing this phenomena ?

When I was playing in dreadspire for the first time about 6 months ago I never saw anything like this, the vampires would always do their fake death thing right at the spot where I was fighting them and not move. So, maybe this is a new thing?

I may make my way back to DSK soon, I still haven't finished it, and I'll tell you what I see.