[HomerJau]

Skin should have no effect on that, but just to quickly eliminate it should you switch to Estuary just to confirm.

The audio play time/progress bar issue is same using Estuary
 

To see if this affects all passthrough types it would be great if you were able to test with DTS and Dolby Digital if you have any music with those audio types.

No problem with play time/progress bar using standard DTS and Dolby Digital audio types in an mka file
 

To see if this is specific to music paplayer could you test video with DTS-HD and TrueHD audio tracks? this is to see if progress bar is performing ok when videoplayer is used. 

No problem with play time/progress bar using any video (MKV) file with various codecs

NEW ISSUE:
Kodi 18.3. Music Videos from DVDs (NTSC and PAL) are way out of video/audio sync. In fact the video appears to play in slow motion. These are MKV videos with DTS or AC3 sound. The same MKV files play correctly on Kodi 18.2. (and all previous Kodi versions since Kodi 15 when I started using Kodi)

EDIT: The issue above regarding DVD sync was solved when I set Kodi's TV setting to 1080p 60Hz (it was set to 2160p 24Hz)

NOTE: All above tests on Kodi 18.3 on Intel NUC with LibreElec (LibreELEC-Generic.x86_64-9.1.001)