This has been reported a few times, but there's an ore spawn in the silver mines that happens behind a wall and impossible to get at. It's located at the southern part of the mines by a bend. Been like this for years.
Also, there's two ores that used to spawn behind locked doors. One behind the locked door at the southern part of the map, and one in the lower cave. The lower one used to be silver, the upper one was probably iron or something before the ore rotation stuff got put in. Now there's nothing there at all in either place.