I’ve noticed that since the iOS 12 update, on my iPad, I can no longer control the selection of a group of words. I can select a single word, the entire post, but if I try to drag the selection handle, my selection jumps to the end of the post. I can’t drag the selection over just a few words. I realize this may be an issue with iOS 12 that is out of your hands, but thought I’d mention it in case you can do something.