Possible solution for the bolt / fracturing issue. It looks like a layer adhesion problem. Has your printing environment changed? Ambient temp? Temp overnight? Airflow? Add a new airfilter or fan somewhere in the room? In any case, question the direction you slice. Just for a moment, consider using a slicer in the Prusa family of the latest versions. Prusa, Bambu and SoftFever. They all do well with hybrid tree supports. Things to consider: Place a slight chamfer(0.5mm) on any layer line 90deg intersections. I mean, anywhere it goes from parallel to the z axis to perpindicular to the z axis (like the top section of the bolt). Just a _little_ bit will really help intercept point stress and cause layer seperation. Those pin holes are almost impossible to keep stress risers out of, without changing print orientation. I hope the reason for current orientation is for ease of printing, and not an already known structural issue that is just as difficult to solve. Link to bolt orientation picture:

Remix^2 from @BooliganCustomGunworks:f USW at home v1