Ouch!

The P-Tab shouldn't be hitting you in the Anus, though it would be close to there where your perinium is. Perhaps you need a different model? Sounds like the current models you have for the P tab don't have it extended far enough for you. Not sure how easy it is to mod the hard plastic. You can try that - perhaps with heating, or some other model. I'm sure others will recommend which one.

I have experienced difficulty getting erections early on in use, but it went away.

I've never heard of the P-tab slipping into the area around the anus, but I would imagine that'd be quite annoying and uncomfortable. I'm thinking that perhaps you are getting lube on the area where the P-tab hits, causing it to slip and slide around? If that is the case, I'd try using some folded tissue paper under the P-tab, that'll soften the pressure a little and soak up the lube so it won't move around so much. Not sure if it'll help, but worth a try.

😕

How in the heck is the "P tab shifting from the perineum into the anus", or even pinching the skin around the anus? I have a hard time imagining how this is at all possible, if you are indeed using the Aneros as it should be.