No picture and cracklings sounds at boot?

Anybody ever ran into this problem, when booting the console, that there is no picture, and there are crackling noises happening?

I got my Dreamcast recapped recently, and it was doing this even before being recapped.

So i'm wondering, if it wasn't caused by the aging caps, what could cause this?

I have a RobotRetro USB-C power board in there, Also a GDEmu clone 5.20.5, Noctua fan mod, clock battery socket, resettable fuse on controller port, red LED power light, thermal pads were replaced as well.

What i know: this problem happened BEFORE getting the board recapped, thermal pads changed, resettable fuse on controller port installed, and thermal pads changed. I don't remember such a thing happening on another Dreamcast i owned, which had another GDEmu in there.

What i might also try is cleaning the contacts for the GD drive/GDEmu with isopropyl alcohol 99%.

Could that problem be caused by the GDEmu itself, maybe developping issues?