Login Issue in CoursePress Theme

I have installed the premium version of CoursePress Pro and the CoursePress Theme as well. Recently I am facing issues that, the site has turned out to be slow and some students cannot login. It's like it may be a problem with all but only a few have reported.
I consulted this issue with my server providers i.e. GoDaddy they are saying that this issue is with the theme. So if they remove the theme everything works good.
Removing the theme would leave the LMS in a bad state with no goo supporting UI.
It would be great if you could suggest something.