The following error occurs at the end or at the beginning of a Synthesis/Implementation run, or when opening a Vivado project:
This issue is associated with a corrupt protocol buffer file (vivado.pb) within a synthesis or implementation run directory.
Deleting the .pb file (e.g., synth_1/vivado.pb) will resolve the issue.
Additionally, recreating the project from scratch or deleting the run in question has also been shown to resolve the issue.
Note: The protocol buffer file is where project and runs messages are stored to allow Vivado to display messages in the message tab and project summary without re-running a process.