3023 is a 1x2 plate. There are two part numbers of 1x2 plates on Mecabricks... 3023 and 28653. But BrickLink only has one entry for the 1x2 plate. Both of these reference the same part number in BrickLink. I'm guessing you've got both of them in your model (and in the same color).

If this is the problem then you can fix it by replacing the dark grey 28653 with dark grey 3023 or vice versa in your model.

If you don't want to do that, then edit your XML file in a text editor. Search the file for 3023 until you find the entries with color 85. (An entry starts with <item> and ends with </item>.) Make a note of how many you need from both entries and then remove one of the entries. Then just make sure you have the correct quantity in the entry that remains.