Illarion.org

again when we went treasure hunting... after finally locating the treasure - the message someone else has already been here - try again later.

This happened twice last night... are these maps permanently damaged.. is there any way to tell which maps are broken and which will still work.. I have many old maps and some new. It is really frustrating to do all the work - and then not have the fun of the guardians, or the treasure.

Those maps are not broken. The message you got is supposed to occur only under very specific conidtions: If someone has digged out a treasure at the very same position but the guardians of it are still alive.
However, this is currently not working and leads to the following problem: If there is ANY active treasure, no matter where, you cannot dig out any other treasure. So there can only be one active treasure at a time.

That will be solved with the next update.

I may have just been lucky, but when I received that message the other night and just stayed put testing it for a bit I got the treasure after a few more attempts. I suspect as most treasure hunts are successful, it is probably worth loitering for five minutes or so while you have the correct position, just to give any other treasure hunter time to finish their business. Might save you a bit of frustration until the next update takes place.