Welcome to the forum, @MikeMcLean. Sorry you’re experiencing an issue and thanks for raising it here.
I’ve tested with each combination of OmniFocus 3.3.2 (v123.20 r329826) and OmniFocus 3.4.1 (v128.9 r335353) and the current Version 1.0 (2552) and previous (beta) version of Hook. I could not replicate the issue. Both macs in my tests are running macOS 10.14.5
What version of OmniFocus and macOS are you using? To simplify and homogenize the testing, could you please ensure OmniFocus has a single window focused on the inbox for starters to see if that makes a difference?