After about 2 months of running well, this happened with the 32 day clock:
I wasn't in the room at the time, but I imagine it was quite dramatic as it was almost fully wound so the weight had a long way to drop. Viewed from the other side you can see the fracture is where the screw that supports the string goes.
Yikes. That is totally unexpected, especially with 4 perimeters and good infill density. All of my newer clocks are using printed hooks.
The only places that uses horizontal screws (along the layer lines) take effort to minimize splitting. The screws used to hold the dial are angled so the stress is spread across many layers. And the M3 set screws use oval holes so they have mostly sidewall pressure instead of top/bottom pressure.