I have a translator who has noticed the same problem on 2 different computers. On her computer, she was running Keyman 10.0.1207.0 and Bloom 4.3.4.
She described the issue as follows: “I’ve noticed in Bloom that on my computer and my translator’s computer, backspace doesn’t work properly - the cursor moves somewhere else when we hit backspace and deletes those letters. So we’ve found that using delete works, but I was wondering if you’ve heard that from anyone else and if it might be a Bloom issue or the Keyman keyboard?”
After updating to the latest Keyman and Bloom, she said, “I did the installs and I’m still having a problem with the cursor jumping and deleting different letters”.
She is running Windows 10 version 1803. I’m guessing that her co-translator (who was also having the same issue) is probably running not running Windows 10, so it doesn’t seem like a Windows version-specific issue.