the original msi contains a few features, where one feature = one file.chm and a few files.pdf. Each is the key of its own component.
The difference between v.1 and v.1.1 is one file.chm, no other file has changed.
When I do a minor upgrade using the full v.1.1 package, the product is properly upgraded.
When I apply the patch (REINSTALL=ALL REINSTALLMODE=omus), the file.chm gets upgraded, but the files.pdf of the same feature get removed !

I have this in the log for the feature:
MSI (s) (C0:AC) [15:46:11:490]: Feature: MyFeature; Installed: Local; Request: Reinstall; Action: Reinstall
And this for a component that shouldn't be involved in the patch:
MSI (s) (C0:AC) [15:46:11:490]: Component: _5113g05f.pdf_2005; Installed: Local; Request: Local; Action: Local
....
ProcessComponents: Updating component registration
MSI (s) (C0:AC) [15:46:12:771]: Executing op: ComponentRegister(ComponentId={12AFD6E3-0821-413F-BB98-AACE08B747CE},KeyPath=C:\Program Files\MyProduct\Sub1\Sub2\Sub3\5113g-05f.pdf,State=3,,Disk=1,SharedDllRefCount=0,BinaryType=0)
....
MSI (s) (C0:AC) [15:46:12:880]: Executing op: FileRemove(,FileName=5113g-05f.pdf,,)
RemoveFiles: Removing file: C:\Program Files\MyProduct\Sub1\Sub2\Sub3\5113g-05f.pdf
MSI (s) (C0:AC) [15:46:12:896]: Verifying accessibility of file: 5113g-05f.pdf
....
Does anyone know what's going on ?
Thank you