Still present in 4.18. When touching a button, the press event is fired.
When the button is released, we receive 3 events: release (which is expected), then press again, then release again.
This occurs in editor or packaged builds, even when “Use mouse for touch” is disabled. We currently employ several workarounds to deal with this but they are becomingly increasingly complex and will not keep us from needing to use custom UI widgets or a custom engine build.