Hi, since posting this i have actually answered my own question, so please feel free to close this thread.
As suspected it was to do with the Share drive. After doing some detective work we found someone external from the project had accidentally deleted our as-built folder entirely and had the IT department re-instate it without letting us know. In the process breaking the link bn our TBC job and where the LAS files were stored.
Safe to say our "Survey" folder is now read only
Cheers