Error when inserting Gallery in WordPress 5

Hi.

I’m inserting a gallery in wordpress 5. Sadly the plugin is giving me an error after that. Giving me these errors. (removed the domain with … )

Uncaught Mpdf\MpdfException: Invalid size representation “calc((100% – 16px)/ 2)” in …wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/SizeConverter.php:35 Stack trace: #0 …/wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/Mpdf.php(19781): Mpdf\SizeConverter->convert(‘calc((100% – 16…’, 167.30155555556, 4.2333333333333, false) #1 …/wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/Tag/BlockTag.php(385): Mpdf\Mpdf->setCSS(Array, ‘BLOCK’, ‘LI’) #2 …/wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/Tag.php(239): Mpdf\Tag\BlockTag->open(Array, Array, 669) #3 …/wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/Mpdf.php(15310): Mpdf\Tag->OpenTag(‘LI’, Array, Array, 669) #4 …/wp-content/plugins/dk-pdf/includes/dkpdf-functions.php(198): Mpdf\Mpdf->WriteHTML(‘ <div class=”dk…’) #5 …/wp-includes/class-wp-hook.php(286): dkpdf_output_pdf(Object(WP)) #6 …/wp-includes/clas in …/wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/SizeConverter.php on line 35

Any help on this? If I remove the images, then there is no problem.

Kind regards
Troels