a theory
Pictures as requested. If the quality is insufficient I can take more tonight with better lighting.
Thanks.
Scott,
Excellent photographs! Those along with the illustrations from the manufacturer lead me to some speculations, a theory concerning what happened. I wanted to see if there was damage to the outside of the ferrule, almost a given if there was the kind of train wreck caused by sloppy set-up or careless work on the tip installer's part. The outside of the ferrule and tip too for that matter seems entirely free of the type of damage I would expect to see if the installer was at fault when trimming the tip. Simplest explanation tossed out the window!
Now looking at the interior, both the photographs and the manufacturer's illustrations: What I see is that there is an unusual amount of load borne by the area where the ferrule is glued to the shaft face and that first little short step that the long tenon goes into. The ferrule has to be out of a fairly flexible material as well as the miracle filler for this to be a low deflection shaft. That indicates that the glue joints at the base of the ferrule and at the short large diameter step are stressed every time a ball is hit. In most designs the structural integrity of the assembly comes from the mechanical assembly and the glues/adhesives only serve to hold the components in place, they don't bear a significant load.
I strongly suspect that the adhesive failed at the line where the ferule joins the shaft on the outside of the cue and in that step area adjacent to this visible area. Then the tiny center tenon takes a heavier load than it was designed for both when balls are hit and when someone works on the shaft.
My guess, you heard the occasional odd sound because of the movement between ferrule and shaft where the glue joint failed and that failure was also the primary cause of the end assembly breaking off the shaft. The long thin tenon may have already been damaged before bringing the shaft in for a new tip also since it was bearing a load it was never meant to bear if the joint failure I suspect actually existed.
My opinion, a questionable design that relies heavily on adhesives that are being asked to bear unusual loadings and a resultant adhesive failure are at the root of your problem. The material of the ferrule could have also failed at a microscopic level where some of it was allowed to move and some was held in place by the adhesive at the base. Unusual demands are made of the ferrule in this design too, don't know if it was up to the task or not. Yet another issue, end grain glue ups of wood are failure prone under load. This design relies pretty heavily on glue ups to end grain. A standard design gets much more assistance from side grain glue up than this design does.
I don't think the repair man bears any responsibility for the ferrule assembly breaking off. If unfamiliar with this design, as I was, the cue man took some things for granted and was burned. He should have caught that this was an unusual construction after it came apart and before his repairs. If he just looked at the shaft and not the piece broken off it would be very easy to not notice however.
I would send your photographs to the manufacturer, I think they should eat some or all of the costs of a new shaft. Anything left remaining, the cue man should cover. He made an error any of us might have made if unfamiliar with that shaft, never-the-less it was an error on his part.
With twenty-twenty hindsight he should have stepped away from the job and contacted everyone involved when the end of the shaft came apart. I have replaced a handful of tenons on conventional shafts and only explained to the customer what I did when returning the shaft however, not that big of a deal on a standard shaft and a well done repair is almost always stronger than the tenon and shaft was to begin with. The cue man's mistake was not recognizing an oddball shaft when doing what seemed a routine job. I could have made the same mistake, I would have covered it but would have taken it up with the manufacturer myself afterwards. I suspect the manufacturer is seeing failures in the area we see in your photographs, the step area I discussed.
Very much my opinion here. My opinion might be different if I had everything in hand to look at very closely under magnification but I think I have built a likely chain of events.
Hu