Hi bretskee and thanks for your reply.
The pins connected are in fact 13, 7, 15, 11. Not 26, 28, 20, 34.
Check the picture attached. You can see the traces.
Regarding the common ground, my board and the raspberry are powered from the same power supply. But I soldered a jumper cable between pin 6 of Pi and a ground of the board.
As expected it didn’t make any difference.
The board and the OSPi program runs as it is expected. No problems there.
The only problem is when my macbook power plug touch any metal near the board.
Today I noticed that even when the macbook power plug touches the metal enclosure of the OSPi power supply, again the relays are acting crazy like in the video.