Had to return my .22 conversion for M-4

I bought a CMMG .22 conversion for my M-4/AR-15 but had to return it. The bolt would not return to the forward position.

Took a look at it with the guy at the gunshop, and we could see that my hammer sat too high to allow the bolt to move freely.

He offered to sell me a new "trigger" which I suspect meant a drop-in trigger assembly with hammer, but I declined. I didn't want to spend $200 to get a $200 conversion to work.

Has anyone seen this before? The lower I have which contained the hammer is a CMMG, which I bought as a complete lower.

It's not a notched hammer. But I could see how it was clearly in the way of the bolt return. Is there an adjustment for how high the hammer sits when cocked?