MacOS: Key from A-Z0-9 aren't acounted anymore

Some time after 2018-01-22, my WP Client stopped counting normal keys from A-Z and 0-9. Only Meta keys like Alt, CMD, SHIFT etc. are counted. Neither the space bar is counted. Mouse and trackpad clicks are still counted normally.

I already reinstalled the client by removing all associated files. Re-enabling WP in the Accessability settings didn't help either.

Any ideas what the problem might be?

WhatPulse 2.8.1 on MacOS 10.13.3 (just updated today, problem persists since 10.13.2)