What can be wrong/broken with DP and DVI of my monitors?

What can be wrong/broken with DP and DVI of my monitors? I have three Samsung SE24E650XW monitors https://www.samsung.com/de/monitors/busi... (manufactured June 2015). I always used them via their DPs. One ist still working but over time two of them started to malfunction one after the other with flickering and switching the signal on/off in arbitrary periods. The final status of the two is the following now: