Regarding used 2015 Ford F-150 problems, perhaps the most notable issues come from the transmission. In particular, there were and still are complaints about the truck slipping out of gear.

The 2018 Ford F150 has transmission issues. It has gear slipping issues and Fors is aware of it and does not stand behind their product. Bought my F150 XLT NEW. AFTER less then A year my driver ...

The Ford F-150 has long been a favorite ... these trucks experienced slipping, erratic gear changes, and even complete transmission failure. Most complaints arose between 80,000 and 120,000 ...

Thumbs up I own a 2017 ford f150 it has multiple problems ... At 51K miles the transmission has become a big issue (e.g. slipping when moved from park to reverse to drive, hesitating to engage ...