Thankfully I found your post! This has been driving me nuts for some time. I actually missed an important reminder today and was late because it no longer plays a longer sound which used to work I guess in Oreo. I set a different sound for loads of options there but I didn't think to try...
Thanks for the tip on the plug-in. I bought Tasker but never took the time to set it up. You're instructions were perfect and hopefully that means no more blinking blue lights when I sleep.
Cheers!