Doubled notes, same voice with update 5.1.80.2224

After updating to 5.1.80.2224, I opened an arrangement I was working on before the update and in the contrabass, I now see this:

I don’t even know how to input simultaneous notes into a single voice.

As far as I can tell, this only appears in these 2 bars.

See attached project:
strange-doubling.dorico (632.3 KB)

Edit: They’re easy enough to delete but I’m curious where they came from.

(You can do shift-I 1)

well, thanks, but that’s not really the point. I definitely didn’t do shift+I … at least not sober. The point is, either I fat-fingered something or there is a glitch in the update – hence me reporting it.