WD MBL - Time Machine Backup Error

I have been using WD MBL for a long time for my MAC Time Machine Backup successfully. However, recently I have started getting the following error intermittently 

“The backup disk image “/Volumes/VibhorTimeMachine-1/Vibhor’s MacBook Air.sparsebundle” is already in use.” 

If I reboot MBL, Time Machine backup starts working normal, however the error comes back after few successful backups.

Hello, see if the following link helps. 


If you refer the link, it talks about Apple Time Capsule setup and recommend rebooting Apple Time Capsule. My setup uses WD…it works for me when I reboot WD MBL but I want a permamnent solution/ identify the problem, as it keeps repeating. I can not be rebooting MBL every few days.