Hello,
On one internal apex server I have added an Interactive Grid region with only 4 columns - the problem is that even though there is enough space I get horizontal scrolling 
I have tried to replicate it on apex.oracle.com and created an interactive grid with data from the dept table and I got another another issue: Toolbar and table header and displayed over the grid's data at the bottom:
https://apex.oracle.com/pls/apex/f?p=16108:1

Apex version: 5.1.0.00.45 in both environments.