The Walter dude in intro went into an anomalous state where he just regged back with big leaps and stayed there in front of me. I tried luring him way out up to the point where he resets but still he just regs. He didn't kill me either as I too regged nicely when my health went below 30% or so. Try as I might, I couldn't get him below 40% before his health jumped back up.

Closed app, went back in and it was totally different. Now he kept teleporting away, no regeneration and was a piece of cake to deal with.