Staying logged in and Keepalive

A user is getting repeatedly logged out while using my site. I have watched her screenshare remotely and she can be in the middle of writing a post or scrolling a page and it hangs and then asks her to log in again.

This is very odd since I have the session timer at 4 hours and the remember me plugin set to 4 months.

I know you've addressed this issue in the forum before, but I was wondering about trying the various session timer countdown extensions, like
Session Keeper
It says "If you have the login module assigned to display on all pages, your logged in users will never see the warning message. This is because the Joomla login module enables keepalive for all pages where it appears. When keepalive is enabled on a page - the warning messages will not be displayed because the user will never time out".
I assume CB Login does the same and I have it on every page, so this extension wouldn't work?

CB does not manage Joomla sessions. If she's being logged out it won't be because of anything CB is doing since we don't manage the session. Either Joomla is deleting her session (check _sessions table to see if it exists) or her browser is.

That extension is for Joomla login module so it likely won't work with CB. Joomlas keepalive is output by CB; you'll notice "JHtml::_( 'behavior.keepalive' );" in CBs login module template files which is what outputs it. Ideally yes you should have a login module set to display on all pages.