fancybox popup opens twice

I’ve an old website (WP3.x) recently upgraded to latest WP.

An issue has appeared that when hitting an image in a gallery (rendered with catablog), the fancybox popup opens twice (i.e. have to hit the close button 2 times, to close 2 fancybox boxes containing the same image). The gallery type used is Make a gallery for all images on the page (default).

Have tried the Revert to defaults option with no success. Have also tried the Use a custom expression to apply FancyBox with the default expression given: jQuery(thumbnails).attr("data-fancybox","gallery").getTitle();. The latter does fix the duplicate popup issue, but at the cost of some/all the styling options from the other tab settings of the plugin not working anymore (Appearance, Animation, etc.).

Here’s the relevant html output:

With Make a gallery for all images on the page (default):

<div class="catablog-row catablog-gallery">
	<a href="https://wptest.domain.com/assets/catablog/originals/print-1-270711.jpg" class="catablog-image fancyboxforwp" data-fancybox="gallery">
		<img src="https://wptest.domain.com/assets/catablog/thumbnails/print-1-270711.jpg" alt="">
		<strong class="catablog-title">My title</strong>	
	</a>
	<div class="catablog-description"></div>
</div>

With Use a custom expression to apply FancyBox:

<div class="catablog-row catablog-gallery">
	<a href="https://wptest.domain.com/assets/catablog/originals/print-1-270711.jpg" class="catablog-image" data-fancybox="gallery">
		<img src="https://wptest.domain.com/assets/catablog/thumbnails/print-1-270711.jpg" alt="">
		<strong class="catablog-title">My title</strong>	
	</a>
	<div class="catablog-description"></div>
</div>

Please advise, thank you.