I'll suggest checking the folder names in the targeted files path for special characters.
I have checked the folder paths. I can copy and paste a working icon (from an existing app) into the directory where the misbehaving icons are and the new app will build successfully. (I use the same naming scheme for my icons).
I did eventually get the images to work, but after converting through ImageMagick the PNG files that were generated by Photoshop. During the ImageMagick conversion it threw the following message:
convert: Ignoring incorrect cHRM white(.28056,.29582) r(.62075,.3401)g(.28308,.5865)b(.13095,.06423) when sRGB is also present `icon_BIG_512x512.png' @ warning/png.c/MagickPNGWarningHandler/1754.
Im not exactly sure, but it seems the source image has some kind of errors, and the ImageMagick conversion removes it. Doing the conversions through Photoshop i could not get the icon to work with Content Builder. It seems that the Content Builder checks that the PNG are accurate, and the image although saved as PNG that i was feeding to Content Builder didnt match the proper PNG specifications. The ImageMagick conversion ignores thus removes the misbehaving areas of the image that did not match the PNG spec.
Shot in the dark...did you save them as interlaced.
Thanks for the suggestion, they are not saved with interlaced option from Photoshop. I think i may have just come across a strange source picture. Never happened before so was curious what caused it and if people in the community have come across simliar problem.