Whenever possible I use the heat-shrink solder connectors for harness repairs.
You can see the issue in your pics where this large number of wires being attached with a solid brass crimp causes failure. The edges of the crimp create a sharp corner that results in fatigue in the wire due to vibrations.
May be better off grouping the ground wires into pairs and tying all those together. More splices but less strain on the wires.