caltic0: I've uncovered all of the map markers and decided to go about and finish the Treasure Hunts, more specifically the Witcher Gear quests.

I've ran into a few problems however. During the Feline Gear base quest, Dahrim Castle and the tunnels beneath Temple Isle do not register that I have found the diagrams. Dahrim Castle has a marker, but the marker leads to a rock with nothing on it (I assume a cat engraving is meant to be here). So sadly, I can not finish this quest without having to use console commands to do so.

This actually also applies to all Hidden Treasure markers on my map. Once I loot the specific chest, the area location (the white circle on the minimap) doesn't turn to grey.

If there's a work around or a fix for this that would be great.

Thank you in advance!

zerebrush: For the tunnels beneath the temple isle (meaning the illusionary wall) you need an item that you will get from Keira.
The second part - later in the game, part of another quest, seems I have forgotten the details here (on my second run now with lots of time gone since I first went there, sorry).

HertogJan: The diagram is in the castle's basement.
You might need the 'The White Lady' quest in order to enter it.
I did that quest yesterday in NG+ and found a diagram there.

As far as Temple Island goes, I don't know. You might have to do a quest first in order to have access to it.

The map marker not greying out is not something I have occurred. Not during my 1st playthrough and so far not in NG+.