Path followed for crash:

1. Placed bottom half slab frame block
2. Right clicked with magenta concrete on slab frame block
3. Server crashed

Here is the crash report:
crash-2021-08-27_15.19.22-server.txt

Yup that's the same problem as #46, #49, #50, #51. I'm still working on it... It should be released in a couple days
Regards, Manu

Fixed with 0.4.0