I am a current student at UC3M, and as long as I know, they do not cut your money without reason. They do it only in few situations, and this is when people fail more than 2 courses in the first year (they will not renew your scholarship for the 2nd year), or they stop attending class.
Not everybody who enters the master is allowed to continue to the Ph.D - you should have the sum of grades above 0 ( A=+1, B=0, C=-1, D=-2 ), and shouldn't fail more than 1 course in the first year.
For those who like Econometrics, I strongly recommend UC3M.