The majority of Glock owners know how to field strip a Glock; few know how or feel confident in doing a complete disassemble. Those that think they can, usually struggle putting it back together and sometimes loose parts. Are there folks out there that can take apart and put back together any Glock...Yep!
Just like I know several who can tear down an engine and put back together with their eyes closed, including myself....I'm not sure I would use them in analyzing/trouble shooting my engine, I'd probably take it someone who has more knowledge. Although Glocks are simple, many still struggle with the details.
I've see several where they have lost the firing-pin spring/caps and lubricate the firing pin channel too much.