Do yourself a favor. Search RJ45 and take some time to read you'll find a lot of stuff. Registered Jack refers to wiring scheme, not the number of pins or positions the jack has.

For 8p8c mod plugs I have used the same tool for years with no problems you just have to get the right plug end for the type wire your putting it on. The last plugs I bought were from ICC. You'd have to put a lot of mod plugs on to wear one out. I'd say you're either not fully inserting the wires into the plug or your plug ends are bad.

Retired phone dude