This is a common issue with cPanel when trying to update
The complete error message :
“fatal: Your RPM database appears unstable. It is not possible at the moment to install a simple RPM”
Reason : RPM database gets corrupted over a while, hence preventing cP from updating.
# mkdir /root/old_rpm_dbs/
# mv /var/lib/rpm/__db* /root/old_rpm_dbs/
# rpm --rebuilddb ( rebuilds the RPM database )
# /scripts/upcp ( cPanel update )