An update to my problem!
After taking out the wires from my PC, using different PSU molex connectors and using different methods, I believe I found my (almost) exact problem.
At the end, with 4 fans:
- tried connecting 1 fan (and using different fan connectors from fan1 to fan5) and testing the screen. No problem.
- Connected 2 fans. success with very minor brightness dimming for full speed. However, hardly noticeable.
- Connected 3 fans. still going good, hardly noticeable.
(Fan4 cable does not work)
- Now I connected all 4 fans using Fan1, Fan2, Fan3 and Fan5 (back exhaust).
Here where the problem occured. if all fans at 40% or lower, the brightness stays the same (with minor dimming/flickers on the right side of the screen, especially where the the number "5" selection at which flickers on that side, slight noticeable at first).
When choosing any fan selection and, as an example for this situation, lets say its fan1 (and tested this on all individual fans when all connected) I increase it to High 100% very noticeable dimming of the brightness, and when I leave fan1 on 100% and change channels to fan2, the brightness comes back only if fan2 is still at 40% or lower (confused me).
if all fans at 100%, well, you can imagine what happens ;p. I lose the sight of right side of the screen including rpms, +/- etc.
and when leaving them all back on 40% .. I can see slight flickers that I noticed earlier (starting from right side) and after 15mins+ the brightness dims to the level where I hardly can see any right side selections, where left side is like having less than 50% brightness.
The root of the problem:
I found out that one of the molex pin connectors from the Commander ft fan controller was loose, and can easily pop out of its socket the pin itself, I tried manually push it back where it made some difference to the brightness when testing it, but the pin is very loosely held that I'd imagine not enough power to power up my Fans that it loose brightness. I'm not exactly sure if thats the cause, but i'm positive in regards it did make a difference when I tried to manually insert it back in socket (while plugged to the PSU Molex connector).
Will check it back at the shop and see if they can fix it. Or atleast see if that might be the cause of it.
EDIT:
here is 2 pics of the commander FT after ~10mins of starting the PC.
one is showing Low rpm and one showing High rpm (took the pic with HDR+ on, but in real life, I cant see the panel unless I shine a light on to see their backside shadows).