After the problem with the last run I diagnosed what the problem was.
One of the Drivers was set for a fairly high current setting.
However to avoid the issue again and to be perfectly honest to make things a lot cleaner I took a Vero Strip Board and put some screw terminals on it thus distributing things a better. I also paralleled up the supply lines with wires so it should be able to carry the current.

I've also created a distribution board for the pulse signalling.

Both of these boards worked well. Note I kept a constant eye on the power distribution board to make sure.

I gradually increased the frequency generated by the Sig Gen and got up to 3.2 kHz which gives 120 rpm.
It worked out well.
I think there will need to be a separate solar cell for the signal collection and transmission. The reason being that the current spikes due to the Stepper Motors might cause problems for the processors and the LoRa transmission/reception.

This will be provided by the separate smaller cells and the lithium cells.

Here is the system running.

https://vimeo.com/manage/videos/659764156