I do not seem to be able to get the warning to work.
Auto Follow After Combat on
Warn if I stop Following on
Seconds Between Strobe follow 1

The follow after combat works fine, but when any on the slave broke follow, I no longer get the warning.
Trouble shooting step
disable all other addon except Jamba
delete the jamba.lua and the bak file from the savedvaribles folder
Launch 2 wow on the same computer,
launch 2 wow on different computer on the same network

I run main on 1 pc and my slave on 2nd pc. I used to run on 1 pc only and I remeber getting the warning when follow was broken.