This is happening to me, with a brand-new 2019 Subaru Outback with H/K and an iPhone 7. When connected with CarPlay via USB wired connection, audio playback skips intermittently, every minute or so. It seems to happen somewhat less the longer a given album/playlist/radio station plays, but it's noticeable and annoying nonetheless.
I have tried soft- and hard-resetting the iPhone, hard-resetting the Starlink multimedia unit (hold the on/off/volume button for 10 seconds or so), making sure both the iPhone and Starlink have updated firmware, trying different authentic Apple-brand Thunderbolt cables, quitting all applications on the iPhone - all to no avail.
Bluetooth audio playback (using the same iPhone) is flawless. So too is radio reception (including HD and SXM - I almost prefer SXM's horribly compressed audio to CarPlay, simply because it doesn't stutter and skip).
Leave it to Apple to sweat the tiniest of tiny details on any number of insignificant, superfluous UI flourishes, and then blow it on basic functional matters like uncorrupted audio playback.
Don't know what to do except complain here, and also to my dealer when I bring the vehicle back for scheduled maintenance under warranty. There is ripe terrain for each party to blame the other - Subaru blaming Apple, Apple blaming Subaru, etc., but my hunch is that this is an Apple fumble - otherwise, why would all the other audio (including Bluetooth playback) not exhibit the same skipping/stuttering issue?
Bla-Bla