Yes, they are on the underside.
There are holes cut through the adhesive, so wherever there is an insert, there is no glue.
I wish I would have seen it prior, and I might have a better answer.
Off the top of my head, I'd probably try some Naphtha on a foam wipe (I fear a Q-tip would leave some fuzz behind along the edge of the adhesive)
If they spray a primer on before applying the adhesive, then maybe it's etched into the surface and would have to be polished out?
Or maybe it's some strange condensation from shipping or storage and it would just clean up with distilled water? (although I doubt this, because it was sealed in the factory bag; and it's only on a few inserts)
With the Pandemic, I've got none of these waiting to be installed, so hopefully someone here has an uninstalled HT and can take a closer look. IMG_20201004_134453 (resized).jpgIMG_20201004_134509 (resized).jpg