Do you place RGB images (recommended) or CMYK?
What is your CMYK policy?
I place a CMYK file that has been DMAXed in photoshop to 302%, so in theory my PDF should not read higher than that anywhere?
Also, I just ran a test placing the same file in RGB and exporting with the same result, random pixels well above what the profile's max is (over 310 readings with the profile max being 301).
A few points that you don't provide us.
Which PDF/X are you referring to? PDF/X-1a (everything dumbed down to DeviceCMYK on output and no live transparency)? PDF/X-3 (color managed, but no live transparency)? PDF/X-4 (the current PDF/X spec with color management and live transparency)?
You don't say tell us whether the CMYK color space of the image is the same CMYK color space as the output intent for the PDF/X file. If they differ, your image will indeed be transformed with a CMYK => C'M'Y'K' 3-4-3 transformation when creating PDF/X-1a or when RIPing PDF/X-3 or PDF/X-4, or for that matter, looking at output preview in Acrobat.
If the color values are shifting overall, that could be a major issue. If it is only a few “random pixels,” the phenomena may actually be artifacts of resampling of your image (in terms of resolution) when creating PDF from InDesign.
BTW, FWIW, best practice dictates that in the general case, you are best off keeping your digital imagery in its original wide gamut color space and converting to the final color space, typically CMYK but possibly including additional colorants such as O, G, c, m, and/or k for expanding the printing gamut, at the RIP itself. That is exactly why we developed the PDF/X-4 and PDF/X-5 standards and the vast majority of modern RIPs (and even Acrobat for printing to PostScript devices) are optimized for this workflow!
It happens with PDFX1a which is the required format
CMYK color space is the same for Photoshop file, Indesign file, output intent
Color values are not shifting overall, it is in sporadic pixels.
I understand best practices, but PDFX is a required file in our profession and these are failing to meet specifications because of this ink density issue. I was suspecting the issue has to do with compression but it doesn't help fix the problem.