DIB Block Entry by database backup job

PLOG has been implemented recently for 9 Production databases, in which, for only one database, DIB Block entry is created by the offline backup job which completed fine.
This in turn abends the backup job for the next run with error:

ERROR-089, Utility not permitted to run

       Another utility has exclusive database control.         
       The following table shows the current contents of       
       the Utility Communications Block. One of the jobs       
       displayed below has exclusive database control.         
       Wait until that job has ended and retry this function.  

Why this happens for only one database? Is there something to be changed to avoid this DIB block entry?

Every backup job will create a DIB entry on the respective database, and remove it when finished - are you 100% sure the backup completed OK ?

Also please note that we are following flash copy process, making database volumes offline in production, and making it up in non production, then the production backup run in non-production.
Recently we have implemented PLOG and running production backup in production itself, after its completion, backup runs in non production.
We get DIB block entry in non production, only for offline backups, not for online backups.
This old process of flash copy process will be retired in few months.
But we are facing this DIB entry issue only for one database out of 9 databases.