blobDelete task remains in "Cancelling" status and does not accept stop or delete

We can’t tell what is happening without seeing the logs. You need to post your logs or you can generate a support zip that contains all logs in administration menu and attach it to a ticket in our issue tracker. You can try by first upgrading to the latest version of Nexus Repository Manager. Also, a friendly reminder, the version of NXRM you are running is known to be vulnerable and we recommend upgrading anyway.