Bitrix: catalog exchange CommerceML

Build a correct CommerceML 2.05 pair from the price list: import.xml (groups + products) and offers.xml (prices + stocks) with stable Ids based on SKU, so that repeated exchanges do not duplicate the catalog. Plus, a diagnostic checklist for broken exchange with 1C: log, PHP limits, encoding, permissions.

Own working stand GuardLabs (not a client order).
Live demo: guardlabs.online/demo/cms-tools/bitrix/