Hi Edward, sorry for the necro post.
For me, I've resorted to stopping the sequence in NINA, then going to my Gemini virtual hand control on screen.
I initiate a Park at Counterweight Down. Then re-begin the sequence in NINA. That usually results in NINA Slewing to the target, but on the other side of the meridian.
Alternately, I can initiate a meridian flip with the Func button on the virtual hand controller. (third item down on the Func button.)
My mount is running the Gemini II version 5.12 I believe.
Where this fails me is if I am before the post meridian by some degree. (Sorry, I'm not well enough versed to now the degrees or technical terms.)
Anyway, that is how I have managed to manually force a flip. (And of course, be awake as well.)
Sonny Edmonds