It has to do with chaning to the other team. Changing back fixes it.
https://forums.playdeadlock.com/threads/drifter-hunters-mark-passes-through-enemy-in-practice-range.120717/post-229908
Can confirm. It's only happening if Drifter is changing to the other team. Staying in the current default team or changing back to the original team will fix the Stalker's Mark spell.
