Hi Beatriz
Have you tested this in multiple browsers?
I seem to remember the boxes resized for me (but I may just be imagining this!) or maybe my text was never so long as yours.
I think there is a logical "length" of text to drag - very long sentences would become very awkward to manage for the learners, so maybe there is a hard limit on the text filed width?
If so, this would be a question for the H5P developers, rather than Moodle forums as I doubt this could be changed within Moodle.
Did you try similar on H5P.org or H5P.com ? This will show whether it's a Moodle limitation, or H5P limitation (I believe the latter).
