An existing checkpoint file is found with contents that do not appear to be for this package, so the file cannot be overwritten ...

An existing checkpoint file is found with contents that do not appear to be for this package, so the file cannot be overwritten to start saving new checkpoints. Remove the existing checkpoint file and try again. This error occurs when a checkpoint file exists, the package is set to not use a checkpoint file, but to save checkpoints. The existing checkpoint file will not be overwritten.