Examine the threads of the flashback arrestor to see if you can find visible damage. The threads are likely repairable with a die (for male fittings) or a tap (for female fittings). Over torquing the fitting could also damage threads, especially with brass being a soft metal.. Though it is brass on brass so it should be less likely to damage threads compared to lets say brass on stainless steel threads. I'm sure you've already replaced the arrestor, but just in case you want to try and save it
