Adobe XD file work very slowly

Absolutely the same issue here:

1. Version 42.0.22;
2. It's happening across any file I open. Albeit most of our files are of similar complexity and size - generally 2 to 6 artboards, each containing a web design. This doesn't seem excessive, and has never previously been an issue;

It's vitally important that this is resolved as swiftly as possible. At present XD is literally unworkable - I click on a page element and the application freezes for around 30 seconds. And other applications become unresponsive as XD is constantly pushing the CPU to 100%.

Can you check in OS Task Manager how many xd active processes you have while operating that file?