I've got two stories like this...
- Way back around the days of Cakewalk Pro Audio 6 or 7 (!), I was swearing at it for ages and ranting on the newsgroups about it. Turns out I had a dodgy SCSI cable (remember them?) which was connected to the audio data drive, so no surprise the one application that hit that drive hard had problems. Egg on face and many apologies (to the Bakers) ensued.
- The house I moved into 10 years ago always had issues with the phones, especially when trying to use the line for ADSL. My dad - ex-telephone engineer - took a look and discovered that the wiring had been done in a ring, not a star, topology so it was amazing it ever worked. He also looked at the aerial connection, and a junction box (splitter) had been put into the circuit. Backwards. So the impedance was all over the place. And as for the (internal brick) wall that a metal/wire checker detects as filled with *something* almost everywhere so that we can't hammer a nail in safely... Turns out the previous owner's brother-in-law was a bit of a dab hand at rewiring. Allegedly. We did wonder why the owners had said they'd had to get a separate 'phone line installed for their home office as the home internet wasn't reliable enough. Maybe they shouldn't have gone to the brother-in-law to sort it out in the first place!