Time machine not deleting Mobile Backups after backing up on external harddrive This is a followup question to Can't find 68GB local backup folder (regular backups on an external hard drive)
I found out that this folder, now 75GB, is my Mobile Backup folder from Time Machine.

From my understanding the local Backups should be removed after making an external backup. However that's not happening anymore. I've used Time Machine since 2007 and never had that problem. 

I did a backup yesterday (27.Feb.) but I still have local backups from the 22.Feb. 24. Feb and 25. Feb. And the folder from the 22nd is 60 GB.

I'm still using El Capitan and backup at least once a week. 

Has anyone encountered something similar? 
Is it save to just delete these folders after an external backup?
Yes. It is safe to delete these backups after Time Machine has finished backing up the external hard drive. You can also disable local backups completely by executing the Terminal command sudo tmutil disablelocal.

I have done this on my laptop because all the content I use is stored in the cloud (Google Drive &amp; DropBox) and on remote private servers independently backed up.