Editor fights with Android keyboards all the time, it's mainly about phrase composition so stuff like autocorrect, autocomplete and whole-word deletion. I'm pretty sure this is a deletion bug.

Some keyboards like to delete via composition (word by word) and some other keyboards like to delete normally (character by character), some other keyboards, instead, like to do both. Our Editor is capable of picking just one method by suppressing the other in a given time window, but if the deletion event extends over the suppression time window the bug can appear.

I'm sorry for the late reply, I couldn't get online yesterday :(