[DRG]

Does this happen after a fresh start up or after a long time open ? It could be that your "heavily modded" OOB has been reworked so many times it's now unstable. That said, the master OOBs would also qualify as "heavily modded" and I have never had a weapon refuse to save but I have had it get a bit pokey after it's been open and used a lot ( "used a lot" as in many hours open ) and the "fix" for that is to exit and restart.

Don