No, I only hear my heartbeat with the ciem’s in. But thanks for the advice.
I think that I have diagnosed the problem for me, and perhaps for others who have problems with custom item fitting. I believe that when they inject the silicone under a certain amount of pressure, that it distends the ear canal in places where it is flexible, and creates a slightly oversized mold in that area - which is then translated into hard acrylic by the iem manufacturer.
The solution that I am going to try (as soon as the coronavirus issue is resolved) is to have my ears 3D laser-scanned (with an OtoScan machine) at a local audiologist. Since the scanner does not touch the wall of the ear canal, this should result in a more accurate mold of my ear canal, and subsequently a better fit for my 64 Audio a18T ciems.
BTW, I have to give a hand to Taron for waking up 64 Audio for me. After he contacted them, they are much more responsive. Thanks Taron!