The 18.xx beta bug reports seem to be closed so I report this here.
If you have Turn Guidance OFF and Off Course Warnings ON you don't get the Off Course Warning when you go off course but do get a Course Found if you go back on the course. This has been reported by a number of users with the production version 18.23 (& had been reported for several beta versions too including using the beta version Screen Recording function to create screenshots each second to ensure the warning was not missed )
I also have some doubt regarding the "Off Course" even with Turn Guidance On, I have not seen it on several rides with Guidance but I could have missed it, will test some more. Definite about case without guidance .