On really problematic interior glass, I've sometimes had to resort to isopropyl (rubbing) alcohol to really cut through crap on the inside, followed by the vinegar / water mix. I use the clean cuffs cut off old pairs of cotton socks with the alcohol, and then newspaper with the vin/water. (Now, newsprint paper can make a lot of very fine dust so, I do all this before I vacuum / Swiff / detail the interior. )
I know the absolute worst mistake we ever made was to use "Fog-X' on the inside of our car glass. What a disaster and we're STILL trying to get it off one or two of the vehicles, year later now! Ugh! (We ABSOLUTELY SWEAR BY RAIN-X for the outside glass surfaces but, we also learned the hard way, "Fog-X' really stands for "fog-your-windows-to-the-extreme"! Hopefully you've never applied Fog-X or else, I say that is the problem. (?)
The previous posters have probably identified your underlying cause but, for what it is worth (or isn't) I particpated in an online discussion amongst some detailers some time ago about this very "recurring foggy windshield inside glass" and particularly cars where the phenomenon keeps recurring on just the windshield and/or front windows only. There was (is?) espoused a theory that there is "gassing" occurring from some of the materials now being used to fabricate dash pads and, there appears to be at least some anecdotal substantiation of this.
Like I said, the previous posters are much more knowledgeable than I (and have given me something to be on the watch for with my own car) but, I am curious: did you have the problem before the new dash pad was installed?