maybe your external DAC can not play the native tidal format providing by volumio.
you can try enable audio resampling option or change tidal sound quality in sources.
and i see Volumio 3.638 is no offical image!
I use 3.638 at few months without problems. Few days ago Tidal connect stop playing. Now after reinstall plays again. After upgrade on NVMe to 3.639 still works.