Thanks for the fast response. I've gdb installed but I'am not familiar with the debugger, don't know what to do.

There's a systemd-coredump, maybe this helps. The printout is:

Process 6039 (Apricot) of user 1000 dumped core.
Found module /home/mark/.local/share/nakst/Apricot with build-id: 40e88fb6f3397490cb3126297c752a06aaf5f226
Found module linux-vdso.so.1 with build-id: 1b5f65732dbffa7abb7873f64eb02bbab1c8b8a5
Found module libXfixes.so.3 with build-id: a9c550a40b8154a3b4b5e2ac182bb50c013c3f18
Found module libXrender.so.1 with build-id: 7ccbfa4c24e93c42fa50dd2e42fa277630f9650c
Found module libXcursor.so.1 with build-id: d936a5db46d8babb0f2cc490df36b6b18a16d8aa
Found module libmd.so.0 with build-id: cd2d2f71b3967ebde30e2aa43b8eb63339020c06
Found module libgpg-error.so.0 with build-id: 3fbec71c67bee60d8aef00697ee187079b0fb307
Found module libbsd.so.0 with build-id: 9a6c72469251e2feb63e175ef5cb944ce6e00df3
Found module libgcrypt.so.20 with build-id: 60a5e524de0ed8323edf33e9eb9127a9eee02359
Found module libcap.so.2 with build-id: b4bf900abf14aabe12d90988ceb30888acb2bcb0
Found module liblz4.so.1 with build-id: a85971851cd059f1af80d553c8e7170d42ec59a1
Found module libzstd.so.1 with build-id: 5d9d0d946a3154a748e87e17af9d14764519237b
Found module liblzma.so.5 with build-id: b85da6c48eb60a646615392559483b93617ef265
Found module libogg.so.0 with build-id: 842412496daf280ca5491dfb6581df5a378b72f0
Found module libopus.so.0 with build-id: 53a29374ac557d631d863d9908ff5bec82f55ba5
Found module libvorbisenc.so.2 with build-id: 5d30e2a713669895dcf3b298ffed2e4ce56121e8
Found module libvorbis.so.0 with build-id: fc9c832676aac541183d1b4774746bec48b66051
Found module libFLAC.so.8 with build-id: 280eaf0c50a65ab561e803707fca2ec714cd28a3
Found module libXdmcp.so.6 with build-id: 6b60f99504aa1d3999ea02a14366d1a39d6c5dcf
Found module libXau.so.6 with build-id: 7089b383cacbfc1760634a3be19a923e51fe3315
Found module libapparmor.so.1 with build-id: 05135bf3304c5a7f40dfeb28b0ce953d78f1e10e
Found module libasyncns.so.0 with build-id: f192c4e5be41e201707cb7a5a962d43de3c675d2
Found module libsystemd.so.0 with build-id: e17e357f3a8e8198b1de01bd084ca319c72d231b
Found module libX11-xcb.so.1 with build-id: 70f2a36d79c623f42fd70fa7ffb06d8877c74f16
Found module libsndfile.so.1 with build-id: 08e2d078caf371d274047899e3526f7e6c0cf611
Found module libdbus-1.so.3 with build-id: 63e8b99215502138cb63afd6d65851a5e837ed49
Found module ld-linux-x86-64.so.2 with build-id: 15921ea631d9f36502d20459c43e5c85b7d6ab76
Found module libxcb.so.1 with build-id: 1bef862a339557aa16c34c7a4b27f8f3aea90517
Found module libpulsecommon-15.99.so with build-id: 1b08226b05ce048ed0fe3891ef46541035535196
Found module libpulse.so.0 with build-id: 71fae00e01a094ea686803e24fbb20a895e77adf
Found module libc.so.6 with build-id: c289da5071a3399de893d2af81d6a30c62646e1e
Found module libpthread.so.0 with build-id: 81f46d553e2f7c999e43c3eede73a822bc8d5d93
Found module libm.so.6 with build-id: a88ef0199bd5e742ebd0c359edf5cb2be0ec08b5
Found module libX11.so.6 with build-id: 37a5d7bbb78e3a99ea8376a7c80ea0c62fe06494
Found module libdl.so.2 with build-id: feca1a24889ea0b8e9d7c72e28766c14e189a2cf
Found module libpulse-simple.so.0 with build-id: 4f0aba6e155cc25985e585b5d498e0f1ab13de35
Stack trace of thread 6039:
#0  0x00007f52773b79fc __pthread_kill_implementation (libc.so.6 + 0x969fc)
#1  0x00007f5277363476 __GI_raise (libc.so.6 + 0x42476)
#2  0x00007f52773497f3 __GI_abort (libc.so.6 + 0x287f3)
#3  0x00007f52773aa676 __libc_message (libc.so.6 + 0x89676)
#4  0x00007f52773c1cfc malloc_printerr (libc.so.6 + 0xa0cfc)
#5  0x00007f52773c50dc _int_malloc (libc.so.6 + 0xa40dc)
#6  0x00007f52773c75f9 __libc_calloc (libc.so.6 + 0xa65f9)
#7  0x0000560f20b76906 n/a (/home/mark/.local/share/nakst/Apricot + 0x7e906)

Prozess 6039 (Apricot) ist abgebrochen worden und
ein Speicherabbild wurde generiert. // means process aborted