Failed to update

This is the second time I have this problem, I don’t remember how did I solve it the first time.
Virtualmin main page displays that usermin and webmin need to be updated.
Both went into troubles and update was failed.
I went to Webmin - Usermin configuration and perform update Usermin (the up blue arrow icon)
Usermin was finally updated.
Webmin configuration hasn’t that option so I went to command line and executed
yum -y upgrade webmin instead of yum -y install webmin as displayed by the automated process from the main panel
And both were done.

Another question: From the same virtualmin main page I see ‘156 updates to system packages are available.’

My system is a web server that is working good.
I am always afraid to update when the things are okay.
Do you have any recommendations?
Thank you.