DT Swiss 370 hub not spinning smoothly in thru axle frame (end caps?)

I have a brand new rear wheel that uses a DT Swiss 370 hub. (From what I understand, the 370 is the same as the 350 except with pawls instead of a ratchet.) I’m trying to use it on a 12×142 thru axle frame. It came with a SRAM XD freehub body, which I don’t want, so I replaced it with a Shimano HG one.

Everything seems fine when the wheel is off the bike. But when I install it and tighten the thru axle to the recommended 10 Nm, the wheel is stiff and doesn’t want to turn. (The freehub part works fine, though.)

It seems like the non-drive side end cap is pressing against a rotating part of the bearing assembly. When it’s off the bike, I can feel the friction if I press on it while turning it. The drive side end cap doesn’t behave like this.

I think I have the correct end cap–it slides onto the axle and gently clicks into place. I measure 142mm from end cap to end cap (eye measurement with tape measure). However, the end cap is shaped like a top hat and the little lip at the "opening of the hat" is a few mm wider than the axle diameter–it seems like it should be the same diameter?

Do I have the wrong end cap? Am I missing a washer or something?

EDIT

Here is a photo of the non-drive side. Everything from the red seal outwward spins around the silver ring.

And here is a photo of the end cap. It didn’t occur to me when I first posted this that it’s not normal to have a "washer" flopping around between the "silver part" and the "brim." This "washer" is actually a "second top hat brim" that cracked off. I just left it flopping around thinking that was normal. But when I remove it, the wheel spins fine.

So apparently this wheel came with the wrong end cap. The DT Swiss support site says it’s supposed to use end cap model HWAXXX00S6333S, but I can’t find that anywhere using Google. Maybe it will be OK to use this one.