That timing belt walk may be from a wonky water pump or idler/tensioner. There really isn't any way I can think of to put the belt on wrong if the other components are installed correctly. VVT on the exhaust cam can be a challenge for folks not well versed in P80.
Robert just posted a vid of one very similar he fixed on his CA trip, it was a water pump bearing failure, and the belt looked almost identical. I lost the engine in ( new to me ) Old Blue when the idler bearing failed and the belt walked through the cover. That belt had 20k on it according to the sticker.
Dr. Abscate has an entire thread devoted to the Bastards of '99.






