Britgirl – yes, that’s exactly what happened. Was confused by the open source page. Thanks.
The display problem: I’ve been searching for the symptoms – it’s like pixelated and about 10% too big in every direction: it’s not 1080p 16:9 resolution anymore (even though that’s what it’s set as in the Windows display resolution settings). Some forums suggested it was a .net framework conflicting with intel graphics drivers. So I tried uninstalling .net framework versions. It didn’t help. Again though: the laptop this happened on is around 5 years old, and this has never happened, until exactly the same time a NoMachine client connected to it. Rational or not, it’s clearly the cause, one way or another, possibly due to included software / frameworks, but it definitely caused it.