Here is a plunker showing the issue. Click the 'X' on the side pop-over to allow the width of the grid change. Note the visibility of the non-locked column headers.
http://plnkr.co/edit/LOR0tKKDnaclwwgio0dz?p=preview
Would it be possible to add a public resize method to the grid component for issues like this? (If one already exists disregard)
The issue is still reproducible with the given example and kendo-angular-grid v.1.2.3
Should be fixed in v1.2.4-dev.201707251109
As suggested by @gyoshev we might need to clip the header content with:
.k-grid-header {
flex: 1 0 auto;
overflow-x: hidden;
}
@rkonstantinov @rusev do you think this can cause trouble with e.g. column menus?
To illustrate:

Observe the column headers during resize.
After giving it some thought, we can skip the need for the overflow-x: hidden if we calculate the layout with flexbox. It will also remove then need to set the width through scripts, and yields better performance. Here is the updated plunker, requires a bit more testing.
Fix shipped in v1.3.1
Most helpful comment
After giving it some thought, we can skip the need for the
overflow-x: hiddenif we calculate the layout with flexbox. It will also remove then need to set thewidththrough scripts, and yields better performance. Here is the updated plunker, requires a bit more testing.