ipad keyboard disappears when switching apps

When I switch apps while writing an email and then switch back to the Ios Mail app, the app keyboard disappears. I have to switch apps to copy some text so I can paste the text into the message I'm composing. If I close the Mail app and then reopen it, the keyboard reappears but this is annoying when I'm copying and pasting several chunks of text. I've tried all the recommended solutions except I am unwilling to reset my ipad to the factory condition. Way too much trouble. I have about 8 email accounts, all being fetched into the Mail app and I don't want to have to start all over by having to add them all back to a new copy of ios

MAIL app. This problem occurs on both of my ipads but not on my iphone MAIL app. The bug I mentioned in another post here regarding highlighting large amounts of text that extend over one screenful occurs on my ipads but not on my iphone. I prefer to use my ipads to compose and edit because the keyboard and screen on the iphone are so tiny that I make typos on the iphone. I hope Apple fixes this bug on the ipad Mail app regarding the disappearing onscreen keyboard.