Welcome to VMTN. :-)
Refer to below VMware KB for this error.
Ensure you have a copy of data you tinker with as required in KB in case you face more issues. If you are not sure or face further issues, it would be best to raise case with VMware Support for a speedy solution.
Why did you use the basedisk without the snapshots ?
If it was an accident I hope you did not use the VM without the snapshots for an extended time period ?