could not throw away exiting file/folder at destination

Hi,
I have a rule that I use all the time (for years) - moving specific pdf's to specific dropbox folders . When the pdf's get updated in their monitored folder they move and replace the previous files in dropbox. Without changing anything in the rule I suddenly I get a notification "could not throw away exiting file/folder at destination".
It may be a permission issue. I tried to fix/re-apply permissions the destination folder with no success. Does anyone know how to tackle this issue?
Many thanks
Ofir
I have a rule that I use all the time (for years) - moving specific pdf's to specific dropbox folders . When the pdf's get updated in their monitored folder they move and replace the previous files in dropbox. Without changing anything in the rule I suddenly I get a notification "could not throw away exiting file/folder at destination".
It may be a permission issue. I tried to fix/re-apply permissions the destination folder with no success. Does anyone know how to tackle this issue?
Many thanks
Ofir