As the title says a frame is changing while moving a cursor in the drawing area. I suppose it's not okay since you can't calmly draw, frames are just changes if the cursor is on the same "vertical line". Also, I didn't notice similar behavior on your videos. I didn't push the "record" button(it's working properly). Shortcuts work ok as well, including "Next/Previous Frame".
I recorded a video, where you can see it: google drive
Here, I didn't push any button, just moving a cursor or draw.
OS: macOS High Sierra 10.13.5
Unity version 2018.2.5f1
Drawing via Wacom Tablet (touchpad same behavior)