How long did the pet sheet take to dry?
Again using Ecosol max ink it dried in a normal time. You could touch it 10 15 min later without issue. I tend to let dry over night and then apply the layer of 751, or any white with a clear adheasive can work.
One thing the pet sheet stock causes is a lot of static when you remove the one side protective film so I try to wipe down with Iso propal (Alcohol). I use a made profile for a banner material so nothing special on the profile end but static and lint can show up more easily in the print.
As a follow up, I tried to remove some ink off a piece with Rapid Remover (as that stuff will take ink off of almost anything) and I was surprised it took a lot more rubbing to get ink to come off so it seems to bite well on the PET film.