Hi @wpdv, we have done more research and found out that there is a clear issue with WooCommerce when an original image from your media library is smaller and with different aspect ratio than the size defined in your WooCommerce store.
In that scenario WooCommerce will try to regenerate the image attachment metadata over and over again on each page visit. This process which generates image thumbnail sizes in WordPress should not be called so often. The error comes from a function called maybe_resize_image
in class-wc-regenerate-images.php
.
It looks like other users of WooCommerce have reported similar issues and it seems to happen up to the latest WooCommerce version 3.5.3.
The easiest fix which we can recommend is to add the following line of code somewhere in your WordPress WooCommerce site:
add_filter( 'woocommerce_resize_images', '__return_false' );
And when doing so you may also want to add one more line which will block WooCommerce background regeneration of thumbnails, as this can also slow down the speed of your store:
add_filter( 'woocommerce_background_image_regeneration', '__return_false' );
We will share this issue with Automattic, the creators of the Woocommerce plugin, as it does affect all WooCommerce users.