We regularly test our offered scanners.
In case the production is altered we also get a new testing device.
So far we never had any significant variations.
Generally the the shipped profile is generated in a way that it will fit all production models.
This means the shipped profile tends to be smaller than the scanner's potential color space.
This means that the minimum and maximum values of the colors will always be met.
Of cause devices change over time and the way certain colors are seen might change.
So an image scanned again on the same device after a few years might look a little different.This might or might not be visible.
Also individual devices might show variations in color representation if compared.
This depends largely on the individual device.
Also as all optical devices scanners are subject to external influences.
Both temperature and humidity can influence how a device sees color values.
An individual IT8
calibration will measure the true range of colors for an individual device.
This enhances color stability and makes sure the scanner uses a controlled and defined color space.
When you contact Plustek
I would assume a few sample scans should be enough to show your issue.