Wonky Baseline Subtracted

I have a rather old (10+ yrs old) CFX96 and it started giving me weird baselines... but only with a certain TaqMan assay, the other 2 are fine... if corrects the Baseline subtracted somehow to give a curve that is at a 45degree angle and most times less rest of the run.... random wells, and random template concentrations. Can post a pic if this forum allows. Thanks