The first one kinda works, but I think it'd be more clear, when used without "selbst"/self, as this would be read to reference the invention instead of the inventor.
On the other hand, that then feels like "yeah, it didn't work. The invention misfired and is crap". Maybe "Erfindungserschafferzerstörer"? (Invention's creator destructor) but that sounds off, too.
There's not really a word that I can come up with that really conveys this meaning. There's a german saying "wer Andern eine Grube gräbt, fällt selbst hinein" (he, who digs a hole for others, will fall into it by itself). Then there's the humorous "Rohrkrepierer" (along the lines of "died in the barrel") which basically means something like "dead on arrival" / that went wrong and didn't work. So it'd be probably something that references one of those, which would make it work culturally?
Alfred Nobel might be considered a runner up, but I feel he recovered his reputation. That and I don't think anyone but himself really was upset with the path his invention took.
I know you wanted a word, but I nominate "Midgley" to be the new word for that. "To midgley something" is to attempt to create something of value that instead only makes things worse. It's an improvement in the negative direction.
It would only be ironic if it were a lifesaving device, for instance, if the creator of the defibrillator went into cardiac arrest by an accidental misfiring of the defibrillator on him.
Irony requires a reasonable expectation of an opposite outcome.
A solar eclipse happening on a cloudy day is not ironic, it's merely unfortunate. A song about things claiming to be ironic actually containing nothing that will qualify as ironic is ironic.
Irony can be used in many situations. I want a German word that specifically refers to this situation. Something like Erfinderhybris; I just slammed Inventor and Hubris together.
Also not sure about a name, but in Greek mythology, there's Daedalus. He built a massive maze, which was then used against him to imprison him & his son. Daedalus crafted wings out of feathers & beeswax to escape the island of Crete, but his son Icarus flew too close to the sun. Melting the wax, destroying the wings, and drowning in the sea.
To be fair, he gave adequate warning to Icarus. The fault with the wax wings doesn't lie in the inventor or invention, but pure simple user error not following the directions.
Not to be confused with segued, which is 'to move easily and without interruption from one piece of music, part of a story, subject, or situation to another'.
Didn't own the company just the sole British distribution rights
edit to add: He lived on the south coast, used and enjoyed the product, and was moving out of the way for a pedestrian on a narrow path and went backwards over the cliff edge. A tragedy that doesn't belong in this thread.