I compared the file [yourjoomlatemplae]/html/com_virtuemart/productdetails/default_images.php in VM 2.0.18 where the fancybox works properly for me ( I have one website with this VM version) with the default_images.php in current version where I have no navigation arrows. They are different.
There is lack of this part of script:
jQuery(".additional-images .product-image").click(function() {
jQuery(".main-image img").attr("src",this.src );
jQuery(".main-image img").attr("alt",this.alt );
jQuery(".main-image a").attr("href",this.src );
jQuery(".main-image a").attr("title",this.alt );
And the following code:
<div class="additional-images">
<?php
for ($i = 0; $i < $count_images; $i++) {
$image = $this->product->images[$i];
?>
<div class="floatleft">
<?php
echo $image->displayMediaFull('class="product-image" style="cursor: pointer"',false,"");
?>
</div>
<?php
}
?>
<div class="clear"></div>
</div>
was changed to:
<div class="additional-images">
<?php
for ($i = 1; $i < $count_images; $i++) {
$image = $this->product->images[$i];
?>
<div class="floatleft">
<?php
echo $image->displayMediaFull("",true,"rel='vm-additional-images'");
?>
</div>
<?php
}
?>
<div class="clear"></div>
</div>
I don't know what exactly was changed because I'm not a programmer but changes are quite big. Maybe there's any shortcoming which causes that problem...