Hello, Greetings to All

I'm having the current issue and can't pinpoint if its development issue or missing configuration in the odoo 14 community edition.

I am currently trying to set up a product (For sale  in  POS)for which i buy in 1 Unit of measure(galons), then sell it in smaller quanitites(100 cm per galon / 128 oz per  galon).

Steps :

 1* I have configured multiple UOM of products in setting 

2* when i got to configure a products UOM it reverts back to the one chosen above, if i manually select it, once saved it reverts to the one chosen above.

Any help is appreciated.