What printer are you using?
You should have proper adhesion using that printer. Using a custom ICC profile of course.
I know, i don't have any issues running banner on my Latex 360 - with my custom ICC profile and curing time.
Maybe try something like this:
ClearShield Liquid Laminate waterbased UV coating
Adhesion is good, just seems a bit easy to scratch... The artwork is very dark though, so imperfections may be more pronounced due to that fact.
Thanks for the recommendation! I will look into that product.