Hi Smartphonica
No, there is no live chat at the moment, I'm sorry.
This is very weird, indeed.
Perhaps it could be due to some kind of conflict with any 3rd party plugin you have.
In order to determine this, you can try to disable all your plugins except WooCommerce and ATUM and try that way. I would recommend doing so on a staging site (if possible).
Best Regards,
Salva.