Agreed, there is nothing worse than putting all your efforts into making amazing beer only to have the dispensing system impart off flavours.
I had that happen a while back. I realized later in my haste I had let the lines sit a few days after emptying a keg. Noticed a dry foam like residue in the lines with a bright light inspection that didn't go away, with regular cleaning. Had to re clean the lines several times.
Now; I make sure to at least run water through the lines and taps as soon as a keg empties, then proper clean and sanitize before connecting the next keg. It keeps the foamy residue from air drying on the inside of the lines; which is so hard to remove afterwards. Not sure about infection (probably) but it sure makes off flavours
Star san, run through and then let soak for an hour at least, followed by rinsing with warm not hot water helps a lot with that, using the plastic bottle line cleaner kit to back flush. I soak the taps in open position and rinse after each keg and every 2 or 3 kegs disassemble, soak, clean and put back together. I tried pbw and coil cleaner even, and the residue still remained but a Star-San soak and flush cleaned out the residue completely.