BTW,
there is a problem in the-events-calendar/public/template-tags/general.php:353
$label = is_null( $args['label'] ) ? _n( 'Event Category', 'Event Categories', substr_count( $categories, "<a href" ), 'tribe-events-calendar' ) : $args['label'];
Because ‘Event Category’ has been translated before using __() in two other places, PoEdit won’t find the plural in _n(). This problem also exists in your .pot-file.
One way to fix this is to add a context for the string:
$label = is_null( $args['label'] ) ? _nx( 'Event Category', 'Event Categories', substr_count( $categories, "<a href" ), 'Front-End display', 'tribe-events-calendar' ) : $args['label'];
I have update the Dropbox file accordingly.