Tabs are transparent when sliding panes is active in the Pane Relief Plugin

[WardUlenaers]

The bug happens when you activate the sliding panes option in the pane Relief plugin.
What happens is that when you have multiple tabs open and scroll through them,
the tabs in the back are visible trought the ones on top.
Meaning that the tabs are for the most part transparant.
This happens in all display modes: source, live and reading
This doesn't happen to other themes so i think its a bug on the its theme.

To Reproduce

Steps to reproduce the behavior:

1. Install Pane Relief plugin
2. Open the command pallet and use the command "Toggle sliding panes (for current window)"
3. Open multiple tabs
4. Scroll through them

Screenshots

Here are some screenschots with different themes

OS

This happens on a Windows 10 desktop machine