Compose window hangs when sending using JonathanKamen send later in dark mode

I tried turning off the add-on and turned off dark mode. I have been successfully using it this way, having to change the font color using font/bkgrnd color control. I have not updated win10 or TB since the last time I used this function. I send out daily emails with findings to a group bcc list. Not complex nor variating. I went to light mode, turned off JonathanKamen's "Send Later" add-on (which is designed and executes well). Process successfully concluded. Turned back on "Send Later". Still works. I prefer dark mode. Documenting for advice and to see proactively if some gap is there in code say for error handling. Thank you, Greg [redacted phone# from community support forum]