Hm, I guess the problem is the unescaped ; in the X-APPLE-STRUCTURED-LOCATION line. I don’t think there is an easy way to work around that. Creating a new calendar without that event like suggested by @devvv4ever is probably the best solution.
Add button "Get it on F-Droid"
Please, add a button “Get it on F-Droid” with a PNG file from https://commons.wikimedia.org/wiki/File:Get_it_on_F-Droid.svg on https://icsdroid.bitfire.at/ and https://icsdroid.bitfire.at/download/ with the appropriate link to the page of your app on F-Droid.
You can find a link in the “ICSdroid is Open-Source Software” section of https://icsdroid.bitfire.at and its sub-pages.
Yes, but the button is is appealing too. On https://icsdroid.bitfire.at/ the “Get it on Google Play” looks a bit lonely on the large gray square. On https://icsdroid.bitfire.at/download/ it is so far “below the fold” and in a different layout that I didn’t notice it. Hence that these buttons, with the same styling, give users of all stores in one quick look all they need to know on what stores this app is available. Understandable that you want a disclaimer since it is a build you don’t do yourself. However, it is a build that is monitored very strictly and openly, so I think you can list it proudly.