Internet explorer not finding right content from multisite

Okay, so this is at weird one.
I only encounter this issue in IE and no other browser.

I have a wordpress multisite installation where I have content on:
example.com
and
example.com/sub-installation

So there is a front page when a user accesses:
example.com/sub-installation

The front page does show up when you access it.
However, the content of that page is supposed to change if the user is logged in.
SOMETIMES that content won’t change when the user is logged in.

When I click F12 and check the Network tab, it seems like the issue occurs because the browser tries to access a sub-page to example.com and not example.com/sub-installation:
issue

When it looks like this the page works as intended:
right

Is there a way to prevent this?

Does anybody know why it only does this sometimes?

I figure that I could just change the URL for the sub-installation, but is there anything else or?

*edit

So, I see that the likely reason I because Internet Explorer is hit with a 304 redirect trying to access a sub-page to the example.com installation, whereas every other browser is hit with a 301 redirect and thus tries to access the sub-installation instead….

Does anybody know why Internet Explorer is the only one receiving a 304?

And what can I do to prevent this?