I had an error D1513 on the same robot that you helped me fit a servo motor to a radial arm drill (January 2020 Controller D42F-A001 a ZX165U robot)
I have looked through your replies on the thread June 24th 2019, and eliminated most of the things you suggest.
None of the brake releases work (1-7), F4 was tripped but it is on now clear and I am sitting with another error (D1512) on all joints (1 to7). I have swopped boards, checked cables, swopped cables and the error persists. There is a small piggy back board (1KV-50) that looks like it may have taken a knock (see 1KV-50 pic) - there was a power surge here that affected 2 of our laser cutters as well. Any further ideas?