Why does my product's date metafield disappear after adding a seventh item?

I added a date meta field that allows multiple values to my product. The documentation states, that it should be possible to add up to 128 items to it. (https://shopify.dev/docs/apps/custom-data/metafields/types#:~:text=List%20metafields%20enable%20you%20to,store%20using%20sections%20and%20blocks.)

When I try to add a seventh date item the metafield container at the bottom of the product content management page just disappears. This happens before i can even select any date from the picker.

Maybe related: When I try to save afterwards I get an error message that some metafield values got validation errors. Did someone already run into this?