placement of MV-1 filter in front of diagonal

I recently completed a refractor project using a 83/500 RR achromat and have upgraded with a crayford focuser and 2" Televue diagonal. Stars appear as textbook airy disks with one sometimes two diffraction rings shown. On nights of steady seeing I have had this scope up to x200 magnification. There is a bit of false color at high magnification on bright objects so I thought I would add a WO minus violet filter. I installed this in front of the diagonal. Optical performance seems to have deteriorated. I lost the airy disk pattern--stars now show diffraction spikes. Further, I can no longer resolve zeta orionis 2.3" companion and need to use averted vision to see Rigel's companion. Both are easy targets for this scope without the filter. I've also tested an 1.25" Orion MV-1 filter attached to eyepieces and this doesn't seem to impede performance. So, does placing the filter in front of the diagonal cause problems I am unaware of?

I suppose the farther up the optical path you go, the more area of the filter glass you use. So if there are defects in the glass, you start to bring them into play more. If the filter glass substrate was of high quality, flatness, homogeneity etc., then I would think it would not be a problem.

How did you get your lens ? I thought the RR lenses were NLA ?