Sections rendering API returning sections: null

Hi all,
We have some strange behavior going on in one of our client’s stores. On a certain market (/en-be), sometimes the Cart API is not working like expected.
We use the sections rendering API so we can fetch the HTML of the cart drawer, when a product is added to the cart. This has always worked fine and is still working fine on all stores using our theme.
However, in this particular store the response sometimes outputs: sections: null.

I’ve seen a few more topics/questions about this in both this forum and in the Shopify Partners Slack channel, but unfortunately without a clear answer/fix for the issue.