Most possibly it’s your theme’s conflict.
Try to switch to standard theme — is it repeats?
The standard WordPress theme does not have a sidebar, so the issue cannot be duplicated.
I am using the Divi theme from Elegant Themes for my website. Has this problem ever come up before for someone else?
As a workaround try to add to your test more text in it’s description.
Most possibly theme’s developers apply the_content filter to sidebar, but this filter should not be applied there.
Current plugin’s architecture relies on single content point in theme.