Some keys do not work on Bluetooth keyboard paired with iPad

I have been using an Anker Bluetooth keyboard paired with my iPad mini since December. It has worked great until recently when a few of the keys/characters quit working. When I press the key for an apostrophe ('), ampersand (&), or left arrow (<), it doesn't type it on my iPad. I have tried restarting my iPad, turning on/off the keyboard, "forgetting" and re-pairing the keyboard. I even got a new keyboard, all to no avail. None of my efforts restored typing those characters. Those characters do work when I paired the keyboard with my phone, so that leads me to believe the problem is with my iPad. I can't figure out why only those 3 characters are not able to be typed. Any ideas on what I can do to fix the problem?