Repairing Carbon Fibre - Carbon Damage & Repair

This seems as good a place as any to ask.

I home repaired the crack on the cursedexploro™ and it's held up fine.

However

I suspect it cracked in the first place because one of the previous owners has way overtightened the clamp. And they have done this because the post slips.
I believe this to be a manufacturing fault with the frame but being the 3rd at least owner of a now home repaired frame, there's no chance of warrantying it.

It uses an annoying wedge to provide force on the seatpost, pushing it back against the flat back on the seat tube creating enough friction that it doesn't move. In theory. Except it does move, bit by bit, with the clamp still way too tight and my winter weight of somewhere around 66kg on the saddle. Can't get more than 5km without the seatpost being an inch lower. I've caked the post in carbon grip paste which absolutely helps but does not solve.
I think the problem is that the surface within the top tube that the wedge presses up against to push a force back against the post, is set too far forward and therefore the wedge is bottoming out on itself before providing enough force against the seatpost but I can't test this.
I tried using a square washer behind the whole clamp just to push it back a bit and the post held in place longer, for about 20km but then the inevitable slipping happened.

So. Suggestions for how I can stop the post slipping? It is not supported by the sides of the seat tube inside, the post can be rocked side to side when it's clamped tight (obviously this shouldn't be happening either)
I'm not holding out much hope of fixing the mechanism so I'm thinking of other ways.
The post isn't round or I'd put a clamp on it where it enters the frame.

I have some carbon and epoxy