Sadly there isn't much I can do here since it is a problem of vtiger CRM REST interface. The problem is that vtiger CRM REST does not support parenthesis in VQL, so when I look for the quotes related to the contact who has logged in (for example), I execute this VQL:

select * from quotes where accountid=xx or contactid=yy

when we search on quotes, this gets converted to:

select * from quotes where accountid=xx or contactid=yy and condition1 and condition2

this retrieves all the quotes that belong to the account AND those that fulfill the conditions and belong to the contact. The correct way to do this is:

select * from quotes where (accountid=xx or contactid=yy) and condition1 and condition2

but we cannot use the parenthesis in VQL, so, short of reprogramming VQL there is nothing better I can do.

I trust this will be fixed in the future.