The problem is when the option "Group Journal entries" in POS configuration
is enabled. If the option is disabled then works fine.

Thanks for the reply.

Were can i find that option? the accounting tab on the product is blank, while trying on the Category i get a error on the upper right corner that says.

Invalid Fields

* Stock Diary

*Entry stock account

*Exit Stock account

but i can not see where this needs to be modified. can you point me where can I find those options?

check your product. if accounts are set on category, check category.