You have the rotation of the router cutter going the wrong way in relation to the front edge.It needs to spin towards the joint front edge not outwards. Either that or you are starting at the rear of the worktop and going towards the front perhaps thus breaking through and chipping it. A decent cutter helps too,must be sharp.
make sure that you are cutting INTO the leading edge, not out from behind as it will blow out. also check the blade on your cutter, is it as sharp as it could be?
check the instructions for your jig, make sure you are using it correctly.
u must have a v sharp bit! and only go as deep as u dare go! n make a few passes on the cut! and u should always work from left to right!- same way that u read a book! if your not doing thing no wonder its not working!
and remember to cut the one joint on the back site! i.e turned over!
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