My new COB driver isn't working

I’ve used a 1200 Watt DC DC CC CV buck boost controller as a driver for my COB led light.

I worked pretty great for a while, until it didn’t…

Although nothing seams broken or anything, I think it’s just fried.
It has a max rating of 15A and 90V output power.
But input power is limited to 15A as well.

My COB needs about 54V 4A coming from a 16V battery. So the battery was delivering about 12 Amps continuously.
But I’ve also tested it at 56~57V, so I think I just overpowered it.
Especially knowing you should divide these Chinese numbers by two, to be safe (and realistic).

So I bought a new driver.

Almost the same, but with slightly better components and rated at 1800W.

I have used the current control to dim the light. And als to soft start the COB for a longer life span.
On the 1200 Watt version this worked perfect.
On this 1800 Watt version however the COB is acting like a strobe light as soon as I trie to cut the current.

Does anyone has a clue how this is possible? And what is causing de COB to flicker?
I think something is wrong with the new converter, but what could that be?
Can it be the capacitors that is causing an enormous current ripple?