I was trying to edit "Text for notice" in the "Notice dialog" as shown in the screenshot below.
More specific, I was trying to get rid of a few words starting from "Join us." While trying to select the text and drag over it from left to right by mouse, the mouse pointer got stuck after I selected a few characters and I wasn't able to select any further.
I can reproduce this, but only on the Timeless skin. In fact, mouse clicking and dragging to select text is broken in all of VE's dialogs on that skin – I also tried selecting text in the "Media settings" dialog (in the caption edit field) and "Page settings" dialog. All text (including static labels) stops being selected after dragging for a few pixels horizontally; dragging vertically works as normal. Shift+click to select also works normally.
Recording of me trying really hard to select an image caption: https://drive.google.com/file/d/1PngcNkK7tnS583MD_yVTSiJJIx-Ja3I9/view?usp=sharing [use the download button in top-right corner] (file is too big for Phabricator)
Sounds like the same thing as T183215 (but possibly compounded further by VE/OOJS specific stuff) which appears to be caused by overflow: rules and the whole floaty layout for the columns. Was planning to fix it by getting rid of the whole float approach entirely and replacing it with flexbox, or something, but then I never got the funding to properly work on any of this, so it's all just sat there.