NAD/Bluesound Grouped Zones out of sync, stopping playing, and/or skipping tracks [Investigating]

Roon Server Machine

I have the core on pretty new Macmini (M1) wired connected and playing it directly to the amp via USB and ifi USB to digital coax converter, and a second device, Bluesound flex2i with a wired connection.

Networking Gear & Setup Details

all wired connections

Connected Audio Devices

I have the core on Macmini (M1) wired connected and playing it directly to the amp via USB and ifi USB to digital coax converter, and a second device, Bluesound flex2i with a wired connection. this is the only group I have

Number of Tracks in Library

playing through Tidal

Description of Issue

I am experiencing delays after a while of playing. if I pause the playlist and resrat it, delays are gone, after a while it comes back. Seems like a buffering issue. I only have for few months now, its been ok for years, its been introduced in one of the latest update. any ideas how to solve this?
thanks