Editors borders disappear when zooming out the browser window

[dafo]

Description

When zooming out the browser to 75% or 50%, some of the editor's borders disappear. If you continue zooming out - all the borders appear again. In my case, in Chrome, the borders disappear when zooming out to 75% and appear again when reaching 50%. In IE11 they disappear at 80%, re-appear at 75% and disappear again when continue zooming out.

Steps to reproduce

1. $("#editor").igMaskEditor();
2. Open the editor in any browser
3. Zoom out to 75% or 50%

Result

The left and the top borders disappear

Expected result

All the borders are visible.