Continuous air leak from air dryer purge valve

I need help can’t find an answer I have 2015 FL Cascadia my air dryer is at primary Tank Bendix ad-is this is my 2 time replacing it under warranty 3 time I had to pay for it first air dryer I replaced lasted about 9 months at first I thought it was my purge valve tried replacing that didn’t help so replaced the whole thing lasted only 6 months I replaced new compressor new discharge lines new air dryer worked for a day and now again I can hear air leak from purge valve what’s tripping me out is no air loss compressor builds air to about 130psi and I hear purge and air continues to leak but no air loss when u shut of the truck it stops turn it back on no air leak until it purge again. It comes and goes what can it be