Hi Fama,
I have not looked into it further for now, it is on my list of pedals to investigate. It would be good if PedalPCB would be able to help us with this issue as both of us are experiencing the same problem with the build. Maybe they already have some fix or workaround available that we don't know about.
Cheers,
Mart
FWIW I noticed that if I dial the Gate trimmer back a bunch, the popping
mostly disappears (there is still a dull "thud", but you might not notice it instantly if you don't know what you're listening for) while I think the guitar signal itself isn't low passed too heavily. And if I turn the Gate control itself down so that there is a low pass envelope filter thing going on, then it seems to be mostly fine. But I don't think it's still working quite as intended, since I haven't read any "Yeah dial the Gate trimmer until you don't get popping" comments or similar.
I did see someone mention they had their DIP switch the wrong way around, but as far as I understand that doesn't matter - it makes a connection when turned on, no connection when off, no matter which way around it is. Plus you used switches instead, so that's probably a false lead.
For substitutions I did J201 instead of the 2SK208-Y and a NE5532 instead of the MCP602, but
@MichaelW did the same things and didn't seem to get any popping so I doubt those matter at all.
I did notice that my LED seems to light up and down a bit slowly and not instantly like most LED's in pedals, although I can't see how that could be related. It's also the first time I've used that specific LED (orange), although I'm not sure if LED's even have the parts necessary to make something like that happen by themselves.