Thread safety

[tbrachkov]

The Apple documentations states that the NSHashTable functions are Thread-Unsafe Classes Developer Apple

Solutions might be adding a private queue for the Noted

[mariusc]

Isn't this fixed in 5d25122? Can you check @NickSkull and close this if it's not an issue anymore?

[dominik-hadl]

We've sort of fixed it - but I saw the issue re-appear at one point. This needs a bit more testing.

[mariusc]

Ok, we'll leave this open then 👍