[LAU] mplayer and mpv both crash with jack from libswresample.so.3?

Hi list, I am trying to work around a problem that I have not experienced in the past (but I can not trace it down to a specific package upgrade): mplayer and mpv both crash when playing back audio files of varying formats (wav, ogg, etc) which have a different sampling rate than jack (tried with both jackd1 and jackd2). The files play fine when using alsa as audio output driver. A gdb backtrace points to usr/lib/x86_64-linux-gnu/libswresample.so.3 which is from Debian's package libswresample3 of version 7:4.3.5-0+deb11u1 I can not downgrade this package to the only other available version (7:4.1.9-0+deb10u1) without removing most of my audio programs. Is this error known? How can I find out more about it, and how could I possibly fix it? Thank you! Peter