Okay. A normal reel has a completely flat top like this:
Or seen from the side:
Some reels, like the one your test tape has been wound onto, have a central hub as well:
Seen from the side, you can see that the hub protrudes. About 1mm each side on my Zonal reel:
...this can cause problems. Adjusting the height of the reel tables in the deck to compensate is one option, but it's tricky to do and if it's adjusted for funny reels like that, it is very possible that it will no longer work properly with normal reels afterwards.