Engines
Yes the u/c was a problem for 8 years from the first tethered hovers to a year or so before entry into the RAF in '69. It was completely solved by Ralph Hooper's idea of a self shortening main leg.
With a bicycle the gear has to be designed so that the main gear takes the intial landing impact loads. This means the nose and outriggers are still clear at touchdown (or should be!). When the main starts to shorten the nose and O/R get in the act and the aircraft stays flat. However after the vertical descent has been killed only the weight remains so the main leg starts to extend again and in the case of the Harrier this puts the O/R back in the air so the thing flopped one side or the other giving very bad ground handling and (because of the aforementioned lift due to wing AoA) a tendency to shoot off the side of the runway especially with crosswinds.
The self shortening leg was brilliant. On touchdown the oil that did the job of absorbing the impact was then fed into an accumulator rather than kept at the top of the leg under pressure as with a normal oleo. Thus there was no rebound from the main leg and so the jet settled wings level. When the main leg next left the ground on a takeoff, its weight made it fall down and fully extend sucking the oil back into the oleo for normal operation on the next landing.