Poll is created without entering question and choice

The only way I was able to reproduce this is by setting Create referenced entities if they don't already exist to on and adding some gibberish into the field when saving a node. Not sure if this is fixable as there is no validation possible when creating a referenced node automatically as you can't enter any data into the entity.

The content is created in a custom way.

Can you elaborate this a bit more? To me it sounds you're setting a value into the poll reference field which causes the entity to be generated.

6 months without any activity