Made by Gino Rossi, apparently badge engineered to Grimac. Anyone that sells or services GR can help.
Your problem will be in the grind adjustment area so pulling anything else apart will be superfluous including touching the grinding plates (burrs).
The thread that the adjuster moves with will be clogged up with old grinds.
Remove beans and hopper.
Vacuum out the remainder of the beans from the inlet throat.
Push lock pin down, and unscrew the top carrier / adjuster (black plastic ring). This is a regular thread, so anticlockwise will unscrew it. Unscrew until it comes right off.
Remove (scrape etc) any pasty bogged up encrustations but DO NOT scratch anything up or use sharp metal implements for this job...anything but.
Vacuum the area, top and bottom grinding plates, and around the bottom plate. Fit a hairy brush to vacum and go around the threads. If the encrusted grinds in the threads dont move, use another suitable method to clear the threads.They are easily damaged, dont force anything.
Refit the top carrier. It should now go down until the plates touch. Back off about half a turn.
Clean out the doser / dispenser. A brush and vacuum cleaner etc.
Grind coffee, and set proper adjustment.
THEN, you will be able to work out of the plates need to be replaced or not.
Hope that helps.
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PS if the grinder came from a cafe or business environment, the condition is par for the course and nothing to be concerned about. Just clean it and it will give years of good service.