BeanFieldGroup for Entity with ManyToMany Collection

Hi All, 

I have the following Entity Structure as depicted in the attachment. The attachment depicts a form for Entity X. This is a very common usecase Company/Employees analogy

Entity X
-------- Matrix Unit [TextField](Required)
-------- Specific Gravity [TextField]
---------Source Values [Grid]<Collection>{Add/Remove buttons}
----------------Property X(Required)
----------------Property Y

The Grid is editble and buffered. So on clicking row I get the row editor which is perfect. 

Currently I have to create several BeanFieldGroup's, one at the EntityX level, Another at the Source Value level (For the BeanItem of Grid)

There is no sync in between these 2 BeanFieldGroups. 

I am sure this is not how Vaadin intended the Validation framework to be. 

I want to be able to check firstly at the Grid row level, that all validators are met and only then Save is allowed. 

Secondly, I would like to check at the Form level, when finally the Entity X form is submitted, it validates the fields of Entity X, INCLUDING GRID ROWS, because a user might have Added a row and not filled any information. Thus creating empty rows. 

Please let me know how can I implement this usecase. Any pointers would be great. 

Also I am using Reindeer theme, which is not showing me CommitExceptions when Validation fails on Save. it just shows a red * and not the validatior message. What Can I do for the same?

I thank you for your help. 
Thanks
Chahat