Hi sodatap ,
Apologies for any inconvenience caused.
I've just tried to edit those fields in a variation using a configuration like yours (BOM Stock Control activated) and they were updated correctly.
Which versions of ATUM and ATUM Product Levels are you using? Have you any additional ATUM plugins installed?
Please temporarily disable all your plugins except WooCommerce and ATUM plugins, switch to a default theme (as Storefront) and tell us if you aren't still able to modify the fields.
Best Regards,
José Andrés