Out of the blue latency in a single project

I was working in my Cubase 8.5 project for a few hours when I decided I to take a break. When I came back (project was still open) I found that there was a terrible latency (+/- 20ms) when I played my keyboard that wasn’t there before my 45 min break.

I shut down cubase rebooted my PC en started the program again… Guess what: still that latency… I opened another older similar project: no audibly latency.

I’m running Cubase Pro 8.5
interface: Behringer Xenyx Control2USB
keyboardcontroller: Roland FA06 (MIDI over USB)

Can I anybody tell what could be causing this?

Plugins with a high plugin delay