ERA before FET

I currently completed one round of ivf, with an egg retrieval and a single embryo fresh transfer. I had a missed miscarriage by 9 weeks in March. I am getting ready to complete a frozen transfer with PGS tested embryo, however, my doctor is suggesting a mock cycle with ERA testing before.

I was reading up a bit on this and it is for implantation failure. I feel like if I got pregnant there wasn’t a problem with implantation?

Has anyone had any experience with this test? It is not cheap at our clinic... with meds it may be over $3,000. I do want the best odds, but I almost feel like they’re trying to take every last penny from us at this point.

Thanks for your feedback!