Roofers torch propane regulator?

I am expecting two new regulators not to leak from regulator to bottle fitting? 1st leaked so did the exchanged one. Each leaked on 3 other bottles so it's not the bottle fitting the regulator fits into.

According to the retailer who sold them to me I am expecting too much and could have used a sealant. The gave a refund refusing to test or give another to try on bottle in my car.

Am I expecting too much what's your opinions you gas bottle users.
Remember these fitting are supposed to be 'dry' fits and no sealant should be used.