Upgrade from 12.1.4013 to 12.1.6 MP5 gives " Client has failed to apply upgrade package, type full version 12.1.7004.6500 filesize 87746767"

We have around 5000 computers of which  100 computer are still with 12.1.4013.4013. We are in the process of upgrading to 12.1.6 MP5.

Some of 12.1.4013.4013 clients, get upgraded automatically to 12.1.6 MP5. But rest give errors

Client has failed to apply upgrade package, type full version 12.1.7004.6500 filesize 87746767.

This group has been assigned with 12.1.6.MP5 Package. Can I add extra packages to the same group,  to ensure that it gets delta updates from the previous version ie 12.1.6860.6400

I have re-started the clients a couple of times to ensure no pending re-boots.

please help me to re-solve this issue.