[JRTJH]

Here's one "what if" condition that may have contributed to the trailer disconnect alerts:

What if, when you were backing that first time and pulled the breakaway cable, while you were reconnecting everything, you "slightly dislodged the 7 way connector" ?? That would (could) explain the intermittent alerts on the tow home. Then, on subsequent tows, the 7 way connector has been properly seated in the truck receptacle, so there's been no intermittent alerts ....

Your issue may not even include the breakaway switch or cable, they are functioning as designed, and the only contribution of the breakaway system is that dislodging of the 7 way connector resulted from accidental bumping of the connector while reinstalling the plastic pin in the breakaway switch, and the next time it happened, the 7 way connector simply wasn't fully seated.....

Just a "theory about why it only happened those times and never has happened again".....