So, I am going to get back into archery, but my bow could use some refining. I last shot it a few years ago, and had issues with the nock getting pinched off the string. Took it to the local pro shop (and I use that term loosely), and the guy said my fat jawed Scott Mongoose release was causing the D loop to pinch the nock off. As it stands, I had him take off the loop, and now I have a bare string with an e button.

So my question is, do I need a new release, or can I have them put on a D loop a little wider, or just shoot off the bare string and have it re-served more often?

The D loop just needs to be tied longer so there is more room for the jaws of the caliper to fit in there.

The best way to do it is to have nock sets tied onto the string above and below the nockpoint, then the D-loop tied on above and below the nock sets so the D-loop won't be pinching the nock at full draw.   If you do approx. half the number of loops above the nock point than below, then the shaft of the caliper will be inline with the arrow when at full draw.

^ That's quite a bit more space than I leave between my knots but I agree that a nockset needs to be tied with  serving material.

I'm going to disagree that a tied nockset is required to prevent nock pinch. A properly tied/tensioned D loop will be tight enough on the center serving that it will not slide and cause nock pinch. I've been shooting loops w/o nocksets for years now with no issues.

I always use tied nock sets as well - they ensure your d loop won't slip and pinch the nock, and when you have to replace the d-loop, you won't have to re-tune your perfect nocking point.

I tied-in nockset makes it a lot easier to replace the d-loop as well.  I don't see that there is a down side.

I have a metal D on my bow and I’ve never had an issue

It was the loop, not the release. I shot a Mongoose XL for years - now I use the ECHO.

learn to tie a d-loop, it is freakishly simple. lots of video out there on how to do it. (If I can tie one, you can tie one)  if nothing else, so you can carry a spare one in the field when hunting.