When I activate the Accent Mode, some other parts of the Intellij UI get duplicated and put behind the tab bar above the editor. When hovering over it it flashes and when clicking on lines in the editor it changes, sometimes I see the file path bar, sometimes parts of the editors' content, other times the footer bar...

Not having a bar visible through the tab bar. ;-)
see summary.
Activate "Accent Mode".
IntelliJ IDEA 2019.2 (Ultimate Edition)
Build #IU-192.5728.98, built on July 23, 2019
Licensed to XXXXXXXXXXXXXXX
Subscription is active until XXXXXXXXXXXXXXXX
Runtime version: 11.0.3+12-b304.10 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0
GC: ParNew, ConcurrentMarkSweep
Memory: 1961M
Cores: 8
Registry: debugger.watches.in.variables=false, git.explicit.commit.renames.prohibit.multiple.calls=false, ide.tree.ui.experimental=false, ide.balloon.shadow.size=0
Non-Bundled Plugins: Batch Scripts Support, CMD Support, com.alayouni.ansiHighlight, com.intellij.ideolog, com.intellij.plugins.watcher, mobi.hsz.idea.gitignore, Karma, com.chrisrm.idea.MaterialThemeUI, com.jetbrains.lang.ejs, ua.in.dej.myEmmet, zielu.svntoolbox
Material Theme UI 4.3.1
Config Files:
options.zip
Oo WTF... ok but it will take less priority than other bugs. Please disable the option for now
That's ok, just wanted to notify you guys.
Not only in accent mode, it's happening for me on any intellij windows that's not in focus
This is also appearing in the menu bar and occurs when focussing on a other window.

Material Theme UI: 4.4.1
PhpStorm 2019.2.1 Preview
Build #PS-192.6262.16, built on August 8, 2019
Runtime version: 11.0.3+12-b304.25 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0
GC: ParNew, ConcurrentMarkSweep
Memory: 1981M
Cores: 8
Registry: run.processes.with.pty=TRUE, bigger.font.in.project.view=true, ide.mac.allowDarkWindowDecorations=true, ide.tree.ui.experimental=false, ide.balloon.shadow.size=0
Non-Bundled Plugins: com.chrisrm.idea.MaterialThemeUI, com.ppolivka.gitlabprojects, mobi.hsz.idea.gitignore, CssAlphabeticalRearranger, de.espend.idea.laravel, net.king2500.plugins.PhpAdvancedAutoComplete, ru.adelf.idea.dotenv
This is a windows 10 problem. Oh lordy @mallowigi good luck to solving this one, when you have a pr in, I'd be interested to see what the resolution is.
@Sylk this is not a windows 10 problem. I have the same issue on Arch Linux.
Most helpful comment
Not only in accent mode, it's happening for me on any intellij windows that's not in focus