I kept falling under the map since alpha. Last time was Beta 1.2.2.0 but I am sure this is still an issue now.

Most comment case is ramps (45 degree grounds on "Sivir Lair" map. The green one with Sivir eggs around) It happens sometime when you use Wings of Ishmir or when you dodge roll you can go undergroud. Sometimes you start falling right after getting underground until you get to "checker ground area" where you cant move. Sometimes you are just under the actual ground, cant get out and keep going a bit "deeper" with every move you make untill you start falling. Once I've managed to get out from underground with Wings skill, Sadly only once.

Is it not an option to make a reset button that would set character position a little bit above the map ground level ? So when you press it you kind of spawn from the air and fall down back to normal ground ?