Speaking as someone who, among other things, occasionally designs custom electronic modules for data acquisition, control, interfacing, etc.
I have to test the PCBs I design when they come back from the assembly plant, and sometimes I do have to debug them - there may be assembly issues, there may be design issues at the prototype stage. Sometimes I have to repair modules that come back from the field - hopefully very rarely. Of course, debugging modules of my own design feels quite straightforward, at least when the design is fresh in my head
Diagnosing stuff other people design on the other hand, I can usually do that given the proper resources, but I'd rather not. I hate it when people ask me to repair their computer, or TV, or whatever. It's hard to explain that diagnosing and repairing these consumer items requires a specialized skillset that, even if it overlaps with my skillset as an electronic designer, is actually quite different. I'm not ashamed to admit that professional repairpeople will usually do a much better job than myself - cheaper, quicker, higher success rate.
This being said, I do sometimes buy defective stuff to repair just as a hobby, or as a personal challenge. But then I don't have a deadline, nobody cares if it takes a few months or years
and nobody gets upset if it doensn't work.