Mercedes aftermarket key blade, not working in door after duplication. Watch this video for the fix.

In this video, we walk you through the process of modifying an aftermarket Mercedes key blank insert to make it work properly in the door lock. Often, aftermarket key blanks are not manufactured to the exact specifications required, causing them to not function correctly in the door even after being cut to match the original key.
We'll show you step-by-step how to identify the problem, modify the key to fit the lock, and ensure smooth operation. This quick and easy fix can save you from the hassle of dealing with a faulty aftermarket key insert, allowing you to use your key as intended.

[@1mikesmiley]

Good info. Especially because Mercedes key codes are harder to get.