One of the major problems the layman faces when using crimp terminals is over crimping or under crimping
over crimping distress the conductor which can cause it to break under crimping has more obvious faults as the wire can pull out
When I simply cannot solder a crimped connection I always use a high quality terminal never those that come in a kit found on the bargain shelf. I also use Klein dimple crimp pliers and for larger cables I have a 16 ton hydraulic crimp set with properly sized dies for each gauge or or diameter of the cable
for making an inline splice I use the barrel butt connectors that allow the 2 ends of the wire to pass completely through this yields a cable to cable contact and can never come apart due to 1 crimp being loose