New to mandolin. Bassist of 25 yrs, all genres, cello for 6 years....played guitar on and off my whole life etc.

New strings on it about 3 or 4 days ago. Played in about an hour or so each day and they just don't stay in tune that well. I tune, play for about 5 minutes and retune. Over and over.

I have really good ears so this is driving me crazy. Also I set the intonation and it's pretty darn spot on but for example my open G is in tune. Fret the 7th fret and it is now out of tune with itself (one of the 2 strings is not matching the other).

Is this somewhat common? It's a flatiron Mando. Sounds great but...is this just the strings still stretching?

The one thing I can think of is that my low 4 strings weren't strung the best (they only wrap around the post 1 to 1.5 times) since it was my first time. The top 4 all came off with no winding to provide friction so I redid those with luthiers knit and they seem a bit more stable than the low strings but they still drift.