Bulk Generate Auto add products not working

Hello there, we are trying to bulk generate coupon codes with the auto add products field. We can generate the coupon codes okay with all the other settings, but the “Auto add products” field is empty after generation.

Then sometimes after trying to add a value in this field after bulk generation, the coupon itself has a critical error and subsequently needs to be trashed. Can you provide some guidance for this? We are keen to bulk generate coupon codes but just can’t get this feature to work.