Some more things I noticed:

You need to remove the datasets cache before testing things, otherwise you might not see the results of your actions after all.
if I add the argument --line_by_line, it goes a while before crashing, before getting an input that’s too long.
I pulled out two very long lines from oscar.eo.txt into a separate file, and it crashed immediately.

It seems the truncation of the input isn’t happening right?