I think youre just misinterpreting the fight with Mando. He's deflecting the blades off his armor, but he still has his body under there, and he's still subject to Newton's Laws.
Secondly, solid is a state of matter, the same as plasma. Nothing makes a lightsaber "go solid", it just eventually encounters resistance such that it cant pass through. If i shoot a hose at a steel plate, the water doesnt "become solid" when it bounces off, it just cant keep going the way its going. We see in The Phantom Menace that dense/thick/massive enough material can provide some resistance to lightsabers.