r/talesfromtechsupport is arguably the best subreddit on the internet if you have ever worked a help desk, supported a family member's computer, or been confused by why a perfectly functional device suddenly stopped working.
The common thread: there is always a reason. It is not always the reason the user suspects. It is frequently the opposite of the reason the user suspects.
Favorites from this thread include the classic 'the cupholder is broken' (the CD-ROM tray), 'the internet is slow when it's raining' (turns out: yes, that can happen with old DSL), and the eternal 'I didn't do anything, it just stopped working' (they did something).