Although not the best looking method of wiring, crimp terminals work ONLY when they are crimped using a proper crimp tool. IN the pictures, it appears that the terminals were crimped with amp pliers, which do not correctly collapse the barrel of the terminal to give maximum wire contact. Amp plier crimps are very prone to loosening up and failing. Proper crimp tools are not cheap but will last forever; I have a pair that I got in 1969 that still work perfectly.

mike in tucson