I really have no idea at all, why this might happen. It is very strange and inconsistent and I didn't find any common pattern. Someone could probably help?

I so far just can give you the code, because I'm not able to identify any relevenat information in it.

Affected example views:

account_fiscal_*_views.xml in https://github.com/odoo-colombia/odoo_advanced_tax_engine/tree/master/account_fiscal_attribute/views