That's a strange one - but I'm afraid that it's going to be tricky to replicate. I've got 11.7 and I think the Command Line interface is only enabled through the licence. I can have a look at the files to see if they trigger the warning through the interface, or test them in DataPump for you. Is it worth trying to edit the script to truncate the lines longer than 4000 characters, assuming Monarch 10.5 is silently ignoring them? Or are there any differences in regional settings that might impact the character set recognition and make Monarch think the lines are too long to process?