Modus diesel rough running

Sounds like fuel pressure sensor issues. Any recent work on the fuel system? Have you checked the sensor's cable and plug connection for obvious damage or looseness?

No recent work. Where exactly is the fuel pressure sensor located on this thing? Is it easy to get to?

It's usually on the fuel rail. Access depends on the engine layout, but it should be visible. Considering the symptoms and your suspicion, and if fiddling with the plug/cable doesn't solve it, a workshop visit could be wise to confirm.

Yep, turned out to be a defective connection. New sensor and labor 95€. Thanks for pointing me in the right direction!