Guy
did you check the environment variable for resampling method?
https://pro.arcgis.com/en/pro-app/latest/tool-reference/environment-settings/resampling-method.htm
Usage notes
- The nearest neighbor option should be used for categorical data, since no new values are created.
Be sure to use nearest neighbor. If your 4 rasters are not perfectly aligned at the pixel level, the software will resample pixel values.
If this doesn't solve it, could you look at pixel values between input and output and give us a specific response e.g. "lower right pixel in the input (last pixel at lower right) has pixel value 13, but in output it's 15..."
Cody B.