I am using the following protocol for making TBE 10x:

TBE 10X : 4 cc

acrylamide: 8 cc

APS: 600 microliter

TEMED: 40 microliter

voltage: 200w for 4 hours

I have applied the same formula for a year and there was no problem. but, recently I am observing bands and the marker scattered all over the gel. and there is no sharp interpretative band. I myself guess it might be due to voltage fluctuation.