I was waiting until I saw the break again to disable the WP-Optimize plugin, but decided to start deactivating plugins to try and find a solution for a ‘Filter by Attributes’ problem I had posted on this forum on, as well (to which you also offered some advice, thank you!).
After disabling WP-Optimize, I saw that it actually fixed the WooCommerce filter, and imagine that it will probably fix the break, as well. Is there a reason for this? Is the plugin incompatible with my site?