Grounding oscilloscope probe effects
Using this op amp as an active filters is not really feasible at this frequency.  Active filter theory relies on the op amp to be close to ideal at the frequency of interest.  At your frequency of 660 Khz, the op amp exhibits a phase shift of -100 degrees and the output voltage swing is also greatly attenuated. Best approach is to build a passive network to build your filter function, then add a gain stage with a high speed op amp.  See the charts from the op amp data sheet: