In the image provided, you can see that glass will render over the inside part of the banner.
I noticed this on accident when I was running around a world and happened to pass through a banner. Have not tested this with anything else besides the stained glass pane it appears.
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Thank you for your report!
We're actually already tracking this issue in MC-167532, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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