I’ve had it replace letters I typed repeatedly, even with slow deliberate attempts. I think a certain letter should come next, and it doesn’t matter if I press a different one, it’s going to put that other letter in. Sometimes after the 3rd time it will get the hint. Other times I have to go back and edit the 1 letter, or actively dismiss the suggestion in the middle of typing.
The other issue I often have is repeated words. I’ll type a word once, but auto-complete will also throw it in there.
I don’t think either of these are sliding issues. I tried manufacturing a slide to see what it would do and had a lot of trouble making it do anything that would replicate the typical errors I run into. Most of the time it tried to start swipe typing. If there was a delay it could start sliding on accents. When I did get it to pick the second letter, it started throwing in extra spaces and acting pretty odd.