Demonstrate a crash in your program and I can take a look. I've limited time at the moment, so can't dig in entirely. So if you have the time todemonstrate the crash and potential propose a fix, that'd be great.
There is no instant crash - it's unusual that a double free() causes an instant crash - it just results in corrupted memory - and sooner or later bad things are going to happen.
The potential fix is to remove the (nonsense) Mfree() from tfork. Greets, Ole