I dunno what to tell you man, as I've noticed the same thing with the films. It burns pretty bad sometimes when i use it intranasal, which is why i don't do so often.
Maybe try another ROA. There are methods people use to make the sublingual ROA more effective. Then there's IV and plugging. I wouldn't suggest doing it IV if you don't have micron filters as IVing the strips definitely isnt good for your veins and a missed shot could mean serious trouble.
Plugging is known to be an effective way to take bupe but many people have qualms about sticking something up their ass.