iPhone keeps removing keyboards I manually add

My iPhone keeps randomly deleting any additional keyboards I add. Any keyboard I add from an app (emoji, bitmoji, and a GIF keyboards, for example) will work fine at first and then a few days later a mix of the key boards will be deleted and I have to re-add them again. Sometimes just one is deleted and sometimes all of them. This has been going on for a few months and I've tried just adding one keyboard individually for a few days and the same thing happens.