500 Internal error after login to whm while updating cpanel

[prakashnplink]

Hello,

This is happening twice while executing cpanel update.

Problem:

1. cronjob triggers upcp script
2. when we visit https://ip-address/whm we see old interface of whm @2011 (screenshot attached ir old_interface.png)
3. after it show new interface and after successful login to whm or cpanel you get 500 Internal Error page (ie login_error.png)
4. checking upcp log /var/cpanel/updatelogs/log.log, it shows normal and updating
5. why is this happending? am I the only one who is facing such problem?

I have attached the screenshot after login to whm

 

[Infopro]

What version of cPanel are you attempting to update from?