Ranking system:
It's Pretty strange .. Last week I was 4k and this weak 80k Really ?
Well I spent much time on it And when i Talk To admin It says
''It's the best ranking system''.
It's pretty annoying.
Disqualification Bug.
It happens In Tourneys (Greykido)
When Someone hits the floor He doesn't lose till The Time end or after a while and I Lost like 4 or 5 times Because of it.

Ranking is based on elo. If the best player has 1602 points, you have 1601 points and there are 80k players with 1600 points, all it takes for you to drop from 2nd to 80k is lose 2 elo points, which can very well happen by losing two games. The rank drops are less noticeable when you attain some more elo points and higher rank.

Disqualification "bug" you're talking about is maxcontacts. Set it to higher value (20) to lower the chance of it (ground contact not registering) happening. If there is an official room with low maxcontacts settings (can be checked with ctrl+g) in a room where it matters, contact a GM and ask him to raise it because it's not supposed to stay low there.