When scaling the canvas, from any value above 100%, the drag handles lose their horizontal centered position, slipping down.
Dependent on windows size and scaling level, it’s possible that they become unusable.
Tested in post and site editor. Everything is up to date.
I can confirm that it’s fixed. Thanks for the heads-up @StrangeTech.
Thank you Cwicly @team for the quick fix 
Hello @Marius and @StrangeTech,
This has been fixed in 1.3.4.3 for the iFrame mode.
Unfortunately, due to the fact that we have little to no control on the actual container elements controlled by Gutenberg, the non-iFrame mode makes it impossible for us to alter them accordingly when scaling > 100%.
The scaling handles will not be visible depending on the scrollbar position, but the scaling bars are still accessible and usable when hovering on the sides of the resizable canvas.
If you run into any trouble, please don’t hesitate to let me know by replying to this thread.
Cheers,
