Custom Molded Earplugs closing off Ear-canal

Wondering if anyone here has had issues with earplugs, specifically custom molded earplugs, closing off their ear canals. I recently got a molding done and went to ACS Custom for ear plugs. When I insert the left ear plug I can feel it close off the ear canal by pushing the skin together. I sent it back to them to have them shave it down, which they did, but the issue still persists. They said they would try again. But I just wonder if there is something about the way my ear is shaped that will inherently be difficult for in-ear monitors and custom earplugs. When wearing in-ear headphones I can push them in and close off my left ear canal while doing the same in my right ear requires more effort/force to close off the canal. So it is mostly just how my ear is shaped. But just curious to hear from others about this.

I don't have issues with in-ear headphones which I wear all the time. I haven't had issues with foam ear plugs, eargasm brand, or earasers brand.

Thanks!