Wonderful addition to the lore of SW.
My main issue is that they didn't really address the question of why the Inquisitors keep finding them.
First, you do not have to worry about spoiler info once the episode has aired. i think most here know better to not come here till after they watch the episode.
Second. I think for now we are expected to believe the Seventh Sister is utilizing the force to track them. The other Inquisitor referred to it as her instinct. But as you mentioned, there might be more to it than that.
My thoughts..
I think there is a hidden beacon. At first, I was thinking that maybe it was in Chopper. The next two episodes are entitled
The Forgotten Droid and
The Mystery of Chopper Base so maybe there is something to that. However they still showed up at the planet once Chopper left. That could be due to they were going by the last trace of the signal they received or the beacon could be else where.
Second place it could be is the Phantom since they used it both times this episode when they were tracked.
I found the lines between Hera and Ezra strange:
How's the Phantom?
I don't know, Chopper was flying.
It just seemed out of place but if it was actually important info that had further implications to a future plot, then it might be a clue that it is either in Chopper or the Phantom.
Last place it could be is in Ezra's lightsaber since the Seventh Sister had it in her possession for a short time. However if it were there, I would think the Inquisitors would have been on their ass all season.
Of course it is still possible that the Seventh Sister has a unique ability to track them. Maybe she feels a special bond to Ezra or Kanan.