Back in the days of the Litton 9 waypoint INS, (where the crew had to insert subsequent WPTS manually as earlier WPTS were passed), I was told by someone who should know that (let's leave the company name out of it; sufficient to say "A South East Asian national carrier's") DC10 enroute SFO to Anchorage turned back to SFO after passing WPT 9 - because WPT 1 (and 2, and 3, and 4... all the way to 9) were still in the INS because the captain, who fancied his chances with a young flight attendant, went down the back not long after takeoff and stayed a little longer than anticipated - without briefing the FO to insert the subsequent WPTS.
When he got back to the flight deck and realised the aircraft was heading back to WPT 1 - south east and not north west, there was insufficient fuel to turn back for Anchorage. What ATC's reaction to this was not included in the story. The captain, a local, kept his job.