Content mode + Safari 8
Content mode uses the flexbox technique is is officially supported since Safari 9 which came out in 2015. (See the browsers which support flexbox.) Because of this, Content mode doesn't work in Safari 8 or older version, as these old browsers don't support the necessary codes for the Content mode. 2015 was a long time ago in browser's development, and these old versions are not even supported by Apple anymore.
If you are using or need to support such old browsers, you should rather build your sliders in Canvas mode which doesn't use flexbox. You should also not use rows and columns.