I really can't mess with the schedule while its running. If you do, at least for me, it crashes the scheduler every time.
I find it difficult to uncheck the "run schedule" box while its currently running.
So to me you have to quickly uncheck the 'run schedule' box (if you can) and then press stop. Sometimes it takes several tries
and with my setup it crashes every time.
But with I just like xlights run on its own, its rock solid.
I've also had problem with the tester also crashing, so I might want to send my 4300+ channel LOR S3 configh to dowdy to examine,
as its likely something in my config causing the instability.