Hello,
After testing, I found that enabling the +999 option generates approximately 2.1 billion items. When duplicate rewards are received, the total can exceed 4 billion items. It appears that this exceeds the game's item limit, causing the items to be deleted or lost.
To prevent this issue, it may be better to reduce the generated amount to around 100 million items instead. I believe this would allow the feature to function much more reliably without exceeding the limit.
I hope you can look into this issue and consider making an adjustment in a future update.
Thank you for your time and continued work on this project.