Keyboard shows up when someone calling

There is a serious bug in iOS 10.3.3 (in my case on an iPhone 5) - when someone calls, the keyboard shows up and blocks half the screen, so that I cannot answer or reject the call. A phone restart temporarily fixes the issue, but after a few days the issue occurs again. This makes answering / rejecting calls (the most basic phone function) impossible. I understand Apple cannot support old phones forever, but given the severity of the issue and the fact that many people have reported the same, I think Apple should address this.

Thanks in advance