On the SQLServer SP3 my stored procedure worked fine.
I have install SP4 and rebuild FT catalogs. I dont delete and create new,
but only rebuild.

Now for example, I entered word 'putin' and 'rasputin'  into table with ft
indexed column.

Stored procedure found word 'putin'
1.select * from dbo.strings_catalog xp where
CONTAINS(xp.*,'FORMSOF(INFLECTIONAL,putin)')
2.select * from dbo.strings_catalog xp where CONTAINS(xp.*,'putin')
and can not find
1.select * from dbo.strings_catalog xp where
CONTAINS(xp.*,'FORMSOF(INFLECTIONAL,rasputin)')
2.select * from dbo.strings_catalog xp where CONTAINS(xp.*,'rasputin')

If I update record
Update dbo.strings_catalog  set name='putin' where 'rasputin'
then ok, this records found also.
After this:
Update dbo.strings_catalog  set name='rasputin' where 'putin'
this record not found.