Came across this thread searching when I had the same problem.

I emailed EHX and was told that there was no fix for this, they advise moving the wires to reduce noise. So I did some trouble shooting of my own. The below pertains to my unit, maybe not yours..

I found that the output jack socket is too close to the PCB. A jack plugged into the unit will pick up the ticking at the ‘tip’ connection even when there is no wires connected to the jack socket.

So ideally you have to move the jack to eliminate the noise. I opted for a rehouse but there are options within the original huge enclosure. Alternatively there is room to add thin shielding between the jack and the PCB, but I’m unsure how effective that would be.

I should note that simply rotating the output jack socket so that the tip connector (quite large on these open frame style sockets) is furthest away from the PCB significantly reduced the noise – this could explain why some units have a noticeable tick and others do not?

Sorry for the necro anyway. I just wanted to post my findings in case it helps others. Noise aside, it’s such a cool box!