Splicing hot tears coring tools up dude...On QR coring tools, if the blade is rough it will not make a clean cut...While JLPS is partially correct, there is more...While loose backnuts can mess your aweep up, it sounds as if you have already identified your problem and it isn't loose backnuts...The only way I have found to get that thin layer out, is to re-core the cable wherever necessary...With a GOOD coring tool...With anyluck the splicer is still there and you can advise him that their coring tool may need to be replaced...