3:30 PM PT -- Another source just contacted us and said it was distance -- which had always been an issue for them -- and not cheating that caused the split.

Kourtney Kardashian sent Younes Bendjima packing recently ... after she said she had the goods he was cheating on her.

Sources close to Kourtney tell TMZ ... Kourtney and Younes broke up the second week of July, shortly after their trip to Italy.

We're told days after that trip, Younes jetted off on another vacation without her and she says that's where he cheated on her ... so she dumped him. The bad blood between them was evident in mid-July when Younes shaded one of Kourtney's booty pics.

The pics of Younes in Mexico this week where he got handsy with Jordan Ozuna were not the catalyst for the breakup ... that happened nearly a month before.

We're told Kourtney laughed off the Mexico pics and said it's just her ex trying to stay relevant.