Automation track only letting me put 2 points on the line

This is weird. I have a vocal clip that I want to raise the volume slightly towards the end. I show the automation track and try to add some points and it only lets me add two points. When I try to add a third it just moves the point closest to it to where I clicked with the draw tool. I have plenty of automation on other tracks that are working fine, just this one track is behaving like this…

Bug? Or am I missing something?

Cheers.

Is the snap turned on?

Tried it on and off. Tried shutting down Cubase and restarting - I found a workaround by drawing a parabola, which adds multiple points. I can then delete the ones I don’t need and move the ones I want into position. But if I try and use the draw point to add single points it just moves the closest one and won’t add a new one. With it only being on one track I’m wondering if I’ve hit some esoteric setting somewhere, but couldn’t find any clues in the manual.