Filtering by many-to-many table
Assuming we are talking about tabular models in SSAS 2012 or 2014 (since 2016 has a new capability around bi-directional crossfiltering) crossfiltering only flows over relationships in one direction. So filtering Status will crossfilter Part, but not Item or Manufacturer. Filtering Manufacturer will crossfilter Item and Part but not Status. 

Any calculation you embed in a Tabular model must be written in DAX. So if you want to filter on Status and have it impact the ItemStock measure you need to code that:

ItemStock :=
IF(
  ISCROSSFILTERED('Status'[Id]),
  CALCULATE(
    SUM( 'Item'[Stock] ),
    SUMMARIZE(
        'Part',
        'Item'[Id]
    )
  ),
  SUM( 'Item'[Stock] )
)


More theory on many-to-many formulas in DAX: 


Optimize Many-to-Many Calculation in DAX with SUMMARIZE and Cross Table Filtering by Marco Russo
Whitepaper: The Many-to-Many Revolution 2.0 by Marco Russo and Alberto Ferrari