Tested on MW 1.28.0, 1.28.1 and 1.30.0
Template parameters containing a table with html tags inside of the cells (<br>, <i> etc) are incorrectly parsed when opening a form. It seems like it's trying to encode the first half of the tags (e.g. <br> becomes <b>).
I have set up a demo page here: https://wikibase.nl/index.php/Page_forms_test