InstallShield (2020) Script debugger stopped to work (running setup.exe /d)

[alex_bond]

all of a sudden debugger stopped to work properly - 

• i run "setup.exe /d",
• it promptly jumps to the function body
• i hit F10 to step over (or click mouse step jumps menu)
• it works few lines, but after that jumps 5 lines down to the if/endif block despite false condition...

i closed and opened install shield; closed msiexec in processes; recompiled exe few times...  same behavior...

any advice on how to fix?  thanks