In mobile view (not the app), using an iPhone4s with iOS 9.3.5, image captions more than one line long overflow and overlap the following content. The same type of error was seen in all articles I visited on enwp, dewp and svwp.
This overflow was not seen using a cellular device with iOS 12.0.1 or Android versions 4.1.2 or 8.0.0.
Can be replicated on browser stack using iPhone+6S 9.0 (Safari)
This is caused by flex: 1 0 100%; rule.
Related/Possible duplicate bug: T207618