Problem with M54 extender and coma corrector.

I have a TSFMA360 focuser that I want to use with a TS 1.0x coma corrector for Newtonian telescopes, so that the corrector can be screwed into the focuser. I  have an adapter to be able to screw it in.The problem is that, because the drawtube of the focuser is short, I can't reach the focus distance. I tried adding an 8mm M54 extension to the focuser, but it has an internal burr in the threaded part that prevents the coma corrector from sliding through it. I was told that this happens with all extenders. Do you know any M54 extensions without this burr so the corrector can pass through? Is there any other solution besides changing the focuser? Thank you very much for your help.

Raúl.