HELP MY DDR MAT lS MESSED UP?

i got it last year but dont use it much but its annoying cuz if u stand in the middle somtimes it gets all weird and acts like ur stepping on one of the arrows,,i think the on or w/e that is supposed to be under the arrow moved up into the middle,,anyway is there anything i can do,and second of all if i get a new one hwo can i prevent this from happening again and is there a brand that is better???please help me