Weird behavior with following mask

[scrnjakovic]

Device

MacBook Pro 2017

Browser (and version)?

Safari 11.1.2

Functional jsfiddle exemplifying your problem:

http://jsfiddle.net/6pco4om7/2793/

Describe de problem depth:

It's described in the fiddle

Thanks for your work, Igor :)

[tclimis]

Also ran into this on Chrome 70 on Windows