Samsung build - Something's wrong.. plz help

So I finaly had the time to build an aluminium heatsink/frame for the strips I got awhile back. I have tested them a few times Ive tested the dimming and everything. It was all fine until today when I disassembled the thing to put some heatsink silicone paste between the strips and the aluminium. Did that, mounted the frame, light it up - only one strip lights up ?!?
Take the thing off the growroom, put it on the table to check wtf is wrong, plug it in again - now only the two strips on the side light up - WTF?!?
Start unscrewing the strips a little bit because I thought maybe I screwed them too tight, plug in - all the strips light up.
I dont quite remeber what I did next, i think I moved the shirt cables that connect them in series to the other side, plug in - again, only the 2 on the side light up.
I've tested the thing many times, It was working fine yesterday.
What am I doing wrong?
Is it possible I have damaged some of the connectors or a connection inside some of the strip or what?
Also I tried to break the connection on purpose by removing one of the short cables and again the 2 on the sides light up. I find this very strange. The line is broken, how can they light up??
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Use a multimeter and run a continuity test on every wire. Make sure there's no unintended ground.

Start at the beginning and work through the system.

Have you tried flipping it and wire the other side? Maybe you got some of that therm glue in a port ??
Also agree with bee, your grounding somewhere
--- is that solid core wire?

Solved it! It was a grounding issue as Beehive assumed.
I had used a M5 instead of M4 washer under one of the screws and I guess its big enough and I screwed it tight enough to bite into the board and one of its connections that runs aroundll the edge.
Good thing that these drivers have all those protections.
Thanks for the fast response guys, I knew I could count on you