There are a few paragraphs I've pasted below where my great-great uncle mentions his father working as a lead engineer on the Steamboat that carried the royal family of Austria around the world. The last paragraph is where he mentions what may have actually happened during the murder-suicide. Is it possible to find corroborating information on this or does something like this just tend to be lost to history?
-- Papa was born a man-of-the-court. In the dining hall of the ship the officers and the engineer of the machines took turns sitting next to the royal highness and there papa glittered because of his pronounced ability as a story-teller, the art of presenting something in a witty way, and because of his tact, also being able to listen, to laugh not too much and not too little. Most of the others did not insist upon sitting next to the illustrious Highness, and rather wanted to eat in peace. And so it happened that they continued to converse with Papa beyond the time he was on tour. Several interesting things- once the ship, upon which the Crown Prince Rudolf rode has the bad luck to ride on a reef, so that there was an enormous jolt just as they were eating in the dining hall. There upon the Crown Prince in great panic screamed loudly, “Just consider whom you have on board, the successor to the throne of our country, a royal prince. You will be severely punished…”
By luck, the ship was freed promptly, but the impression of such cowardice was devastating to all who heard this. Many times various generals of the court came along. They wore spurs like all high officers of the land. The sailors found it comical that at any remark or assertion of His Majesty these generals responded not only with “Very well, Majesty”, but at the same time all clinked their spurs together gently as they bowed slightly. For instance, it was something like this:
Crown Prince Rudolf: “I believe we are going to have nice weather today.”
The Court General: “Yes, indeed, Your Majesty, I also believe that the weather will clear up.”(Accompanied by a gentle “Tschinn” of the spurs.) Again and again a gentle Tschinn.
From several sources out of the train of followers Suite Papa heard the truth about Mayerling, because of which it becomes understandable that the Kaiser said, “Every rumor is better than the truth.” Rudolf bid farewell to the Baroness Vetschera, with whom he had associated for quite some time, who wanted to become empress, in the upper room of the palace. In despair over this in this significant moment, she cut everything off with a secretly hidden knife. Scream with pain he believed in was possible to attach and heal up “the thing”. But the hemorrhage advanced and therefore he shot the girl and himself. This explanation was entrusted to him (Papa) under the greatest seal of silence at that time. That this presented the truth could be realized because several gentlemen, independent of each other told the same story. --
TLDR: Crown Prince Rudolf may have had his willy cut off by his mistress.
Edit: Here is a link, page 1 page 2 to the the original German text - neat sketch included.
There are several things to consider when translating a primary source. The most important of these, for your purposes, is that it doesn't matter if the events are true, so there is no absolute need to confirm them if you cannot / don't want to do the legwork. This is not to say that confirming them might not make an interesting footnote or add to commentary on the piece, and there is always personal interest to consider, but the value of a primary source is that it gives genuine insights into the experience of the author, and can therefore provide modern readers with information about the circumstances that shaped those experiences. Whether the events described in your text are strictly true, a persistent court rumor, sensationalism in the media, or something else entirely, it is the description of those events alone that holds the importance. It is then the job of historians to determine exactly what is going on in this source, and how it fits with sources that have previously come to light.
This being said, if you do want to pursue this lead-and why wouldn't you?-I would recommend starting by reading one or two recent and authoritative books dealing with the Austro-Hungarian court at the time of the Mayerling Incident, or thereabouts. Seek out and contact the author(s) to not only get their opinion, but to find or make a list of those present at the court during the incident. Then, go to the Österreichischen Staatsarchiv and read anything you can get your hands on regarding the incident, especially the letters of those at court. Family archives might also be significant, so, if you don't find everything you're looking for at the Staatsarchiv, try contacting descendants of the individuals for whom you are looking. Then, whatever you find, lay out your findings as a companion to your text. Remember that, though it may be disappointing, disproving the events described in a source is just as important as proving them. Best of luck.
This is not a direct answer to your question, but this previous post by /u/jezreelite may be interesting to you and give you context for this anecdote:
Do you know what he was referring to when he wrote that "she cut off everything" and "he believed it was possible to attach and heal up 'the thing'"?
EDIT: I guess I overlooked the TLDR.