The only things I can suggest:

Close all applications on your phone
Delete pairing from phone and from head unit
Restart phone
Re-pair phone

Try streaming again. Use some 128kbps files and see if they skip. Or skip less.

This may help, may not. There are a lot of variables so very difficult to point at anything specific. Need to experiment quite a bit to find out what works, or what makes it worse. I.e., Phone position relative to the BT antenna can be a factor.

Once you have some data, might help track down the root cause.

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Current
2015 BMW F800 GT, Montego Blue
2012 BMW X5 Premium, Vermillion Red
2008 BMW 535xiT, M-Technik body kit, Monaco Blue
2004 BMW 525i Premium, Olive Green.

Past
1991 BMW 750iL, Alpine White.