finally we found the correct solution:

after you remove file from the DB, you have to backup log

this reset the sys.database_files table

now we successed to add files ...

I reset the services - not help.

I can re-do this "alter database ...remove file" and this leaves the rows in the sys.database_files !!!

OOO !!!

I don't know what to do

I am using sql server 2012 Std. Ed. and I have the same problem.

any idea ?

I am using sequence, and the values are jumping as well.