Not able to update products or create new products after migration 1.7.7 -> 8.0.1

[WorldShisha]

I encountered a frustrating issue I have been trying to solve after migration to 8.0.1. All database files are there and the shop is working perfectly. However, when trying to update product (quantity, description etc) the update fails. Can also not create new products. The error message in debug mode is attached. Anyone any idea? The database seems fine and I can update direct through database, create new products.