t.map is not a function when saving custom section

Hello,

We have made several deliveries between environments for a customer and after all of a sudden it seems, we have an error message pop up when we try to save the record of a certain custom section:  t.map is not a function It happens regardless of what is saved in the custom section record.

I will attach a picture showing the issue. I will also attach a pic showing the error in the console.