Oh no, sorry to hear some of you are having issues previewing on 8.9
There must be some edge case we missed that’s causing this 
Hopefully we can work out what it is and get a fix out shortly. In the meantime you can rollback to the previous version, 8.8.3 from the release notes page.
As @Elixir said - Please let us know what system you’re running on, ie. macOS version + hardware, and a test project that exhibits the behaviour would also be good.
You post it here or email it to: dan@realmacsoftware.com
As soon as we know what the issue is, we’ll get it fixed up and shipped ASAP!
Thanks
Dan