Gas leaking out of the hole of the fill valve

After I fill a gas magazine for ASG P-09, gas leaks out of the tiny hole where the gas from the bottle enters. I verified this by putting the tip of the gas can back onto the fill valve lightly, and it doesn't seem to leak. I've been able to fix leaky magazines in the past by soaking them in oil or even replacing the o-rings but, I have never come across this issue. I already tried to unscrew the fill valve and put Teflon onto the threads and under the o-ring, and it did not fix the issue. Also, the problem seems to be with the fill valve itself, because I screwed it into a different magazine, and the problem still persists. Does anyone know how to fix this?