Gate noise on KA3525
These are comments, really, but I need to show you some pictures so I have to put them here as an answer.
Your schematic diagram doesn't seem to be correct.  There are several points that don't make sense:

The MOSFETs don't appear to be connected to anything.


The drain goes to the transformer, but the source just snakes around and connects to the drain through a capacitor.

The transformer connections are nonsense.



Pin 1 is marked &quot;NC_1&quot; - NC means &quot;not connected,&quot; but you have it wired to something.
The PRI pins would normally be used in pairs - PRI+1 and PRI-1 in use together or PRI+2 and PRI-2 in use together.
There's no match for PRI-3.


You have DC going into the transformer (or maybe coming out of it.)


Pin 1 of the transformer is connected to Vcc of the KA3525.  Pin 1 is &quot;NC&quot; so I have no idea what that's supposed to do.
I can't tell you what's wrong with your circuit, but I can tell you that you can't use that diagram to troubleshoot it.
If your transistors are getting hot, then you must have them connected in some way that isn't shown in the diagram.
Correct your schematic, and then we can see what's going on.
Simply check everything in your circuit as it is built against the circuit diagram and correct the diagram to match the real circuit.
In doing so, you might find the actual cause of the problems, in which case you could correct both the diagram and the real circuit.