some flac streams choke and stutter with flac 1.5.0

i'm sorry i dont have a lot of debug info to go on here, hopefully someone takes interest and digs deeper:

recently some streaming stations became unlistenable for me with choppy audio in mpd so i began looking into it.
serveral attempts to work the problem out in mpd led nowhere, it seems to be an issue with flac.

the nearest i've got to debug output is the following from mpv:

Invalid audio PTS: 0.256000 -> 81.493333
Audio device underrun detected.
[lavf] Linearizing discontinuity: 0.256000 -> 216.530667

both mpv and ffmpeg seem to recover from the errors and play the stream, unfortunately mpd does not, disabling flac support and letting mpd decode with ffmpeg has the result of listenable audio, but has other downsides..

these are two stream sources that consistenly demonstrate the issue:

http://radio3.radio-calico.com:8080/calico

http://mediaserv38.live-streams.nl:8006/live

many other flac streams play just fine. happy to provide any assistance!

Start by reproducing the stutter with the two stream URLs using FLAC 1.5.0, then compare the behavior with mpv and ffmpeg. Trace the streaming decode path responsible for the reported timestamp discontinuity and underrun; done means identifying and fixing the FLAC-side cause and confirming both streams play without stuttering.