I jinxed myself. Now I have a water heater problem.

Just a couple days ago, I replace a toilet in my rig and needed to use a plastic right angle (male) adaptor to my older PEX (the grey stuff) female connector.

With everything being plastic, you'd think there wouldn't be a problem with leaking but this union of white to grey plastic did. No amount of tightening would stop the leak.

So I used some teflon plumbers tape and the leak stopped.

And that's what I suggest, teflon plumbers tape on your drain plug. Even if it's plastic.