Sometimes total "demolition" of existing product, and starting all over (from scratch) is the best way to do something right.
Is that what I understand you did here, dmetalmiki?
Well yes and no, I ripped out all my modification wires, As I could not remember were in heck they went, and what to from years past.
Then I "plumbed in" a new whelen alternate and combined headlamp flasher unit. (Wig Wag).
To try to eliminate all the rear lights brake lights and turn signals from operating at the same time I had to re think the wiring modification for my truck from scratch.
It took me over 7 hours!. I was getting really frustrated and disappointed, and about to give up, When I realised that with my glasses on I could not see close up to wire in the 12 small posts on the unit.
Without my glasses everything was blurred and I kept seeing double!.
It took MANY attempts to put the right operating wire into the right terminal.
Finally, Everything worked.
The headlamps worked on normal driving high and low beam.
The 'Wig Wag' And simultaneous headlamp flashing sequence
worked correctly.
Tired out I quit for the day, Happy and satisfied.
I thought I saw a shadow as I went out of the barn and locked up.
Next day..F.a worked!!
T'was MURPHY I had seen in the shadows.
Ho Hum..Tomorrow I will try again......
But gratifyingly the rear Red Spot lamp alternating Wig Wags do work fine again and correctly.
The wiring in the pictures is ALL trial and testing circuit wiring before substituting it for new final cable and harness cover insulation.