HI, thanks.
Only tried a different USB port, not cable. Will check.
There are no issues playing any conversion (up to the 24/96 limit of my DAC) whilst not in exclusive mode.
When in exclusive mode, upsampling causes popping. Normal playback, without upsampling, whilst in exclusive mode is also fine (inc. for MQA streaming and playback of 24/96 files from the hard drive).