I reran the steps posted in Protocol/1 (Used to capture screen to file) which has never required a pressing of the space bar when leash(-all) is active. I even noted that in the steps.
Now it requires me to press the space bar when leash(-all) is active.
EDIT
I un-installed my current version of SWI-Prolog on Windows, checked that there were no other versions installed, e.g. 32-bit, installed 8.0.0 stable (swipl-8.0.0-1.x64.exe) and reran the steps for protocol/1. The space bar was required. 
Seems leash(-all) is working as it should.