The borders are still there when the Improved app rendering is turned on.
Created a new app to test it. Checked whether the Improved app rendering was turned on, which seems to be turned on by default. When turning it off the borders are gone.
was this on a phone ? (in that case is it an android device or an ios device ? )
also can you give us the powerapps version this app is using ? (you get that from the app detals page in the portal, https://web.powerapps.com)
Can you give us more information about the devices used (make, Operating system version)
also did you publish it again in 3.18075.22 ? it shouldn't auto upgrade the version unless you open it in the studio then save and repuplish it
I did republish the app myself, sorry for the confusion.
The devices used are a Samsung tablet with Android 7.0 and a OnePlus phone with Android 8.1.
I also tested it with an iPhone, everything showed correctly, without the edges.
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