I'm curious to know where you got replacement washers from and what size you went with since I might be doing this on my 21s in the future.
Just as mentioned above, Ask to have a second set of washers fitted when you send it in. Since washers seem to be the holy grail for some reason I would do this every time I send a knife in.
That's how I had an extra set to replace mine in the PJ31 I just received last week. Hope this helps.