"Dependent file not found" issues

I recently have been having repeated issues (with Studio 2019) with projects that were sent to me by the customer. When first opening them, everything is fine, when I want to carry on working the next day, I get a message "Dependent file not found" followed by a path. It seems like on closing the project some files get removed from the Temp folder and are then not found the next time the job is opened. Any solution on how to fix this?