I just ran the 18.2 and 19.1 Studios side by side and I don't see what you are reporting. I can use both help systems as usual. As Andrew pointed out, this may be virtualization hitting you because the index for one system would not work for the other. You can determine if that is the problem by doing the following...

  • Look for DataFlex.chw (that's the help index) and delete all instances
  • Pick a revision and run the Studio as administrator, launch the help and goto the index tab
  • Make sure the .chw file is created in the Help folder for that rev
  • Do the same for each DF revision