It's weird how there are bugs that transcend specific implementations. Wolfram Cloud, Google Colab, Juno (Jupyter for iPad) and Pythonista all have the bug that when you click on a textbox the text sometimes randomly jumps to another location. Maybe the Platonic form of a notebook has the bug too.
(TBH I find Colab such a mess it's kinda hard to isolate one feature and call it a bug. The whole thing is a whole mess of overlapping and intersecting messes.)