Just a guess: There's a lot to be evaluated in the current context. Open up the Data Viewer and see what's being evaluated.
The data viewer list the fields on the current layout. It also list fields from other tables that are mentioned in the script but the values show as <Unrelated Table>. Finally it shows values of variables. Does that help?
Hi Which version of FileMaker are you using. There were a number of complaints about this when 12.0v1 came out. Currently 12.0v3 is available. Not sure if there is an improvemtment on this issue.
One thing to try: For scripts that will be doing a lot of work I create blank layout and use them in Form view. No fields at all. When the script runs it won't download additional records or populate Unstored calculation fields. This can greatly increase the speed at which a script runs. Possibly using this method may help your debugger issue. Note Find, your record set and go to next/previous record along with set field all work the same way they would if the fields were on the layout.
You note above indicates that the Data viewer shows fields from unrelated table. On the Current tab it should show you fields that the script will use. If the Script changes layouts, the unrelated table field may be available on the other layout/context. If the script is trying to access a field in an unrelated table, this may indicate a problem. you should check into it.
I was driving ahead to deliver the current version of my project before taking the time to install the 12.0v3 upgrade. After reading your message I installed the upgrade and my problem immediately went away. Now I can step from one line to the next in the debugger with no delay. Thanks.