I made device panels for my MS2000, Nord Lead2 and TritonLe.
I have the same issue, I have lost some amazing sounds due to this little bug.
My work around is saving the patch before I close Nuendo. If I remember that is...
Next time I load the song the panels are all set to default, but at least my sound is there.
Not sure if that will work in your case.
Seems like this feature/functionality has been left at the door some time ago.
Haven't seen or heard of any updates to device panels in many years.
I can't even edit panels in any version past Nuendo 5.
As soon as I try to open a panel for editing, I get cascading error windows in all versions after 5.
Win7Pro 64Bit, i7 3770k, Gigabyte Z77-UHD5, 12gb Corsair (1600Mhz), Nuendo+Nek 6.5, Reaper 4.591, Studio One, Raydat, UAD X 2, UM-3EX, Glyph eSata Audio Drive, 6TB Storage, U-He ACE, Arturia Moog Modular & Jupiter8v, Korg Legacy (MS-20, MonoPoly, Wavestation), Portico 5043/5033.
AKG 414-B XLII (Matched Pair), AKG D 112, Neumann TLM-193, GrooveTubes GT-66, Shure SM-81 (Pair), Sennheiser e604 (3pack), SM-57 (Many), Beta SM-57, AT-3035, Many More, Panasonic DA-7, Event 20/20p, Alesis Monitor One, Philips MMS321 Multimedia Speakers, TLAudio, HHB, JoeMeek, dbx, Moog Model D, Nordlead 2, Korg MS2000, Triton Le, Boss Dr. Rhythm DR-55, Sound Gizmo, Acoustic Drum Kit, Fender Stratocaster (USA), Ibanez EXSeries Bass, Laney VC-30.