I have a basic MultiLineEditableTextBox on my HUD that has not been modified or scripted in any way. When I deploy to my iPad and then tap on the textbox:
Thank you for reporting this issue. I have been able to reproduce what you have been seeing in the 4.6.1 version of UE4. I have also tested this build on our latest internal promoted build and this issue is no longer occurring. At this time, I am unsure as to when this issue will be resolved in a released version, but the issue is no longer occurring. I will be sure to keep you updated if I here anything about this fix being implemented into a future release.