I received the following inquiry via email:

I haven’t noticed any issue with the flex PVC fitting in the couplings/joints I’ve used. (You should be able to get a good feel for how tightly my joints made up by watching the example video in the article.) If you are sure the sizes match, then I suggest taking a sample to the hardware store where you bought the components to see if they can offer an explanation.

I’ve never had that issue, either. Could it be you’re screwing in the fittings too far? They shouldn’t have to go on very tight to make a good seal on the washer.

As a side note, I’ve had issues with the spigot PVC fittings leaking from time to time. Usually, however, as long as the leak is very small (i.e., doesn’t affect the pressure so much as to compromise the sprinkler coverage and doesn’t cause my gut pain from any waste), I let it ride.

I hope you’ll come back and reply here if you find out anything useful in your search. Good luck!