I was once on a Lufthansa A346 and a couple of minutes after take off there was clearly something not quite right. Slight vibration, just odd. Anyway the pilot announced that the nose wheel doors hadn't closed so he was going to lower and raise the wheels a couple of times otherwise we would have to return. The attempt failed and after about an hour in the air we returned to FRA. The flight was only 3.5 hours so the plane was light and there was no issue with dumping fuel or a heavy landing.
Turned out there was a loose bolt, it was fixed quickly and we were airborne again within 45 minutes of landing. I have suffered worse delays without a technical issue.
The best bit was the guy near us who had gone to sleep with an eyemask on. When we returned to FRA, he woke up and oblivious to the announcements assumed we had landed at our destination..