A lot of physics quackery comes from engineers.* Their knowledge of advance physics is generally nowhere near that of a physics PhD, but their title lends them credibility to many people.
I don't know about physics, but a few years ago here in Argentina there was a epidemy of "engineers that solved the Goldbach conjecture". A few (¿maybe 5?) of my math Ph.d. students friends had each one his/her own engineer with a different unrelated proof.
The histories where all different, but generally it was a long (100 pages) proof that was involved and not very clear. So the math Ph.d. student and the engineer meet weekly for one year to try to understand the proof. It was very painful because they have to understand which part was only unclear or has only small gaps, and which parts had errors that were impossible to fix. And then they had to explain that to the engineer, that were happy to had solved the conjecture.
All of this is in a scientific field that there isn't too much money, press coverage or social prestige involved (not like a "cure for cancer"). So I think that in more applicable fields the problem is worse.
* I have not found the reverse to be true.