The problem with the Osprey was it was too big of a technical risk..... ...that is why it was canceled several times before it every began... ...then after it did get started, Clinton got elected and the Osprey, as well as many other programs, was put at idle for 6 to 8 years, they cut the money but didn't want to see the jobs cut, they litterally gave them just enough money to keep people employed, but not enough for them to do anything to actual make progress on the program...
This resulted in running short of money in test and development, which resulted in some rather dumb decisions in the test program, taking the approach that it is an established helicopter there didn't need all the testing of an entire revolutionary aircraft. That is behind several of the crashes during test and development.
As well, the Osprey, like the F-22 and F-35 made several design choices that push the limits of practical technology to get the desired performance. Things like doubling hydraulic system pressures and electric system voltages, which makes for smaller and lighter actuators and motors. But also makes for more hydraulic and electric system problems as they systems are running at pressures/voltage higher than anything before. That and design was behind one of the test and development crashes.
I knew two of the test pilots that died in two separate crashes, one was the asymmetric vortex ring state crash, the other the hydraulic failure with erroneous indications crash.
The Marine Corps has nearly 3 times as many V-22 as the Air Force, so that is one explanation for the higher crash rate, as well the Marine Corps typical has a higher crash rate than the Air Force in general. I had heard nothing about training problems, other than the typical training teething problems with any new aircraft, which the Marine Corps field before and faster than the Air Force, so they would suffer that initial training teething.
Yes, it was political, two kinds of political. The actual politicians that just want to cut the defense budget, that don't want to replace outdated equipment, that go even more nuts when you try to replace it with even more expensive equipment that is revolutionary instead of just an off the shelf cheap newer conventional helicopter. The other was more it was controversial within the Military and supporters themselves, which ended up in folks dividing up into the Fan Bois/Haters camps.
In a way, the V-22 is a boat/car, it does both fixed wing and helicopter, but like every boat/car, its not a very good boat nor a very good car. So yes, its limited in its fixed wing performance and its helicopter performance. But just like the 1st Gulf War, in the 2nd Gulf Force, the first force to show up in theater in sufficient numbers with sufficient equipment to be a credible force was the Marine Corps (yes, others did show up sooner, but in to small of numbers and too lightly equipped to be any kind serious threat). And the only way the Marine Corps was able to accomplish that in land locked Afghanistan, was with the Osprey. So, harp all you want about it not being such a great helicopter nor fixed wing aircraft, it is able to take off from Amphibious Assault Ships, travel with the speed and range to move the better part of an expeditionary brigade ten times farther than it would be possible with previous conventional helicopters. And then land those forces in unimproved fields like a helicopter.