Slow track loading macOS 11.5 and Tidal via AS 1.5.7

After eventually getting UPNP playback working with the macOS 11.5 upgrade and AS 1.5.7, now having issues with very slow track loading when streaming from TIdal.
Track starts to load very slowly, and when playback starts, it has not buffered sufficiently for the track run through completely. Stops while awaiting further buffer, then continues.
Network speed tested at 50/50 - so no issues there.
Streamed Lossless from Apple Music - no issues
Streamed from Local NAS, loads immediately, so no issues there either
Could it be Tidal servers are an issue today?

Further to this, I am seeing issues with the Tidal app (macOS 11.5) with slow loading of tracks, but the issue does not appear on Amarra Luxe (Amarra fully loads, with no buffering).
I have also read reports that this issue does not occur with Roon either.
Could this then be an issue with the way Tidal and AS preload the stream from the Tidal servers?