Successful FET After MC?

Hello! I was wondering if anyone has experienced a miscarriage after a FET with a PGT-A normal embryo, then gone on to have a successful FET without changing much in your protocol?

A little background: I experienced a blighted ovum with a “normal” embryo after my last transfer. I then took all of the pregnancy loss panel testing and the only thing that came back positive was MTHFR a1298c. My doctor says it’s not helpful because he’s already had me on extra folic acid and a baby aspirin as part of my protocol (however, I’ve done my research and have switched to folate), so he doesn’t know what caused my miscarriage. He suggested taking the KIR+HLA genotype test that’s done in Spain, but it takes at least a month to get results back, which we might not get in time before my next transfer in July. His plan is to have me take extra meds (which would be the treatment) “just in case” while we wait for results and stop them if my results come back negative. I don’t like the idea of taking extra meds if my body actually doesn’t need them, so I don’t want to go this route (and it doesn’t help that these meds are $4000+ alone).

So basically, the only thing changing for my next transfer would be that I’m taking folate instead of folic acid. Has anyone had a successful FET with the same protocol as one that resulted in a miscarriage?