🚀 go-pugleaf

It depends on whether or not the frame in question is eligible for the command. To eliminate the error, you could do:

try
fit given frame to content
end try

This will eliminate the error and work on any eligible frames while leaving the others unchanged.

Does that do it for you? Or do you need to make those ineligible frames fit? If so, then you either need to roll your own break out that frame from its story, along the lines of:

tell mySectionTitleLevel2Frame
if count of frames of parent story of it >1 then
set myNewFrame to duplicate
delete characters 1 through -1 of it
delete it
else
fit given frame to content
end if
end tell
try -- in case 'myNewFrame' doesn't exist or is wrong type
tell myNewFrame
fit given frame to content
end tell
set myNewFrame to 0
end try

But you've now broken the frame out of its group, if it were in a group.

Dave