You should not have tools inside the breaker panel and breakers aren't held in with fasteners. Maybe you can post a picture of the failure

 

Correct, breakers are not mechanically attached. There are two bus bars in the panel and in this case two lead screws per breaker. These are the screws I'm having trouble with.

 

Properly torqued screws and lugs should not be loosening, especially that often.

 

To preface, all is good right now.
Agreed, I had the breaker looked at first by a licensed electrician. He was confused why the bus and lead screws were so loose. What prompted his visit is we had two breaker repeatedly tripping. He found no shorts, no opens, just the loose lead and bus screws. He let me know that if the problem persisted after it would likely be the two breakers have worn themselves out.
Well, it started up again so I just replaced the breakers. After I had them in I checked all the screws and they were loose again.

 

I’d torque them to spec and be able to tell Siemens yes, they were torqued to spec.
And see what they say.

 

I have my doubts if your electrician actually torqued to spec.
Unless you saw him with torque wrench in hand.