4k external monitor, MacBook Pro, and "random" frame-rate drops: what do to?

Hi all,

Thank you for reading this. Firstly, my setup:

• MacBook Pro 2015 Retina
• DELL 27 inch 4K monitor (S2127Q)
• MiniDisplayPort to DisplayPort connection

Issue:

Sometimes I have frame drops when:

• Opening new tabs in Safari
• Scrolling through messages in iMessages
• Swiping between pages

A restart tends to fix the issue, until it happens again in a couple of days.

Any help is appreciated.