My decades old Brass Berzomatic torch developed a leak years ago. I've taken it apart and can't stop the leak. The only way I can stop the leak is to remove the head from the cannister. Been doing it several years without a problem. That sounds like the same behavior you're experiencing. It sounds like your leak is downstream from the tank.
I didn't mean to come off like you make no sense, just that didn't make sense because my tank leaks when it's hooked up, not visa versa.Makes no sense ?, I am over 60, been doing heat and air repair for 45 + years have a license to install gas lines ect , either the gasket on the grill is bad or the valve it's self is. I repair refridge and freezers full time along with hot water heaters and small ac units, I have 20 years with the same company so I ain't plum stupid lol , mistaken sometimes though