A2, welcome to pain. A couples of things after reading your code:
- `--panics:on` is not for "debugging". It's there to prevent catching defects.
- You can't pass `ref object` to another thread without using `std/isolation`,
and if you try and can't then you will have to give up `ref` altogether and
start to use `SharedPtr`/`UniquePtr`/etc (
https://github.com/nim-lang/threading).
- `--mm:orc` is not thread-safe, so use `--mm:atomicArc` (and NOT `arc`!) and
ensure you don't have cycles.
- please stick with `-d:useMalloc` until you have NO crashes.
- please dont use  `fusion/matching`, it doesn't work reliably with recent Nim
versions.
- you can drop the `{.experimental: "caseStmtMacros".}`, case macros are no
longer experimental.
- good luck