Triple check the Plug.
I find that the ones for solid wire tend to have 3 prongs per blade with the center one slightly offset. That way the solid core of the wire gets trapped and doesn't role away from the blade. The pins with only 2 prongs are for the stranded copper. The 3 Prongs do work better on Stranded than the 2 prongs on Solid. If you stick with the right plug for the cable wire type, ensure you see copper at the end of the plug before inserting into the crimp tool, and firmly press the cable into the crimp before and during crimping your success should be well above 95%
Also make sure the you are not using a CAT6 plug on a CAT5(3) cable. The AWG is larger on CAT6.


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