Invalid memory operation during allocation with `new`

[Per Nordlöw]

On Monday, 13 January 2020 at 23:06:01 UTC, Per Nordlöw wrote:
> Unfortunately that didn't tell me the cause of the problem but 
> only the stack trace of the failing call to `new` which is not 
> called inside a destructor.

I found the problem. I was greedly using the `__monitor__` slot 
of some classes in order to get one extra word of class storage. 
Setting it to `null` in those classes' destructors made the 
memory error go away. Thanks anyway for valuable input.