see https://www.beddinghotline.com/beddinghl/component/virtuemart/sealy-posturepedic-grove-city-cushion-firm-detail.html?Itemid=175
you can notice custom filed are showing as many options are there, why
we had migrated from 2.5 to 3 and now using latest joomla and migrated vm2 to vm3 and seeing that error
why and how to solve,
Solved: Just change the List to No in custom filed and that worked.
In the tools is a button to remove them.
The reason is, you have a lot derived products and you had to overwrite in vm2.6 ALL customs. Now you can decide per customfield. In fact, written for people like you. you will love it.