Yes, this is a known issue which will be fixed in version 4.4.1. This version will be tentatively out in mid-February. You can watch the progress of the work on this issue here: https://bug.javlin.eu/browse/CLO-10101
. The workaround is to type the cron expression manually or to use some publicly available tools like this one: http://www.cronmaker.com
to generate the expression and then copy paste it into the scheduler.
I'm sorry for the inconvenience.