The only thing I can think of is the layout is wrong. In my experience, some of the schematics are wrong. My guess is intentionally. It took me a couple of weeks to figure out why the reverb was operating in reverse.
Strip board is a lot easier to troubleshoot IMHO. No hidden traces. What I like to do is take a pic of the back side and zoom in on it. You can see bridges and bad solder joints easier.
If it will take card stock, you’ll have no issues. I used to use my exwife’s printer when she wasn’t home. She was always confused when it ran out of toner so quickly even though she hadn’t printed that much. 🤣
I love it. I wish I still had the old Peavey Bass head I used to have. It was one of the MKI heads. The uncle that gave it to me borrowed it and gave it back when it stopped working. I held onto it for about 20 years before I got rid of it. Wish I had it back.