When a reset_run impl_1 -noclean_dir command is issued on any project after Implementation, subsequent reset_run impl_1 commands do not actually reset the directory and no error is issued. Additionally, when a re-run of implementation is attempted, the following error occurs:
[Common 17-36] Cannot write file ['project.ucf']
This error occurs because PlanAhead tool creates a copy of the projects constraint files in the impl_1/.constrs folder. These .ucf files are marked as read only and cannot be edited/changed.
The workaround for this issue is to take off the read_only permissions on these .ucf files in this folder.