Using a GDB debug session I get this in my Rack log (no GDB trace)
[1178.446 fatal adapters/standalone.cpp:49 fatalSignalHandler] Fatal signal 22. Stack trace:
22: 0x0
21: raise 0x7ffb10bbabe0
20: abort 0x7ffb10bbf1e0
19: wassert 0x7ffb10bbd210
18: ZN4rack6engine6Engine24updateParamHandle_NoLockEPNS0_11ParamHandleExib 0x7ffab0370340
17: ZN4rack6engine6Engine17updateParamHandleEPNS0_11ParamHandleExib 0x7ffab0370510
16: ZN17PatchMasterWidget4stepEv 0x7ffa9ea9b620
15: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
14: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
13: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
12: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
11: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
10: ZN4rack2ui12ScrollWidget4stepEv 0x7ffab03812d0
9: ZN4rack3app16RackScrollWidget4stepEv 0x7ffab035b500
8: ZN4rack6widget6Widget4stepEv 0x7ffab0388ce0
7: ZN4rack6window6Window4stepEv 0x7ffab038aed0
6: ZN4rack6window6Window3runEv 0x7ffab038b910
5: ZN4rack6window6Window3runEv 0x7ffab038b910
4: ZN4rack6window6Window3runEv 0x7ffab038b910
3: ZN4rack6window6Window3runEv 0x7ffab038b910
2: ZN4rack6window6Window3runEv 0x7ffab038b910
1: BaseThreadInitThunk 0x7ffb10587360
0: RtlUserThreadStart 0x7ffb116fcc70