Products without display node get incorrectly updated / displayed

I think this is an issue with this module. But I am not 100% sure.

If you try to use variations without display nodes, various actions (such as adding this variation to the cart) seem to cause PDM to add the product variation id to this field.

I initially came across this when experimenting with using products variations as sub products of another variation. When PDM is enabled, it causes the behavior above even if the PDM page is not accessed (and I can not figure why PDM is even getting involved). Turn off the module and everything is ok.

The bug part seems to be that PDM is updating the Product Reference field, even wen not on the Display page. It surely should not be touching the database at any other point than dragging / dropping with the display page (or perhaps when a variations is added / updated).

I needed to remove this as it will soon be a production site and this is too risky. So I can't test more. I will try this out on a different test system if the module is still being maintained (as I'm not sure about that either).

As well as causing these issues with the variation, PDM then does not display them at all.