For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Out of interest: did you run the latest Joomla version on your test setup?
Fileupload element is displaying fine on my Joomla3.2.4/PHP5.3.8/Fabrik3.1 latest Git
I don't know if Joomla is updating to J!3.2.4 or J3.3 on PHP5.3.10 (tech requirements is saying php5.3.10+, so 5.3.10 should be included in J!3.3)