Facing an issue updating a discount metafield with my custom Discount Function UI extension

Hello all,

I have created a discount function and UI extension within the admin that allows for creating highly customizable free gift promotions. The promotion data is stored in an app metafield which is passed through to the function. However, the need arose to expose this free gift promotion data publicly so that it can be accessed outside of the context of the app. So I updated my logic to also write to a public discount metafield when creating/updating the custom discount. Everything has worked well with creating new discounts within the app, but I recently ran into the following error when trying to update one:

It has happened with 2 discounts that were created via the app on Oct. 13, but I have not been able to replicate it with any new discounts. I can re-create the discount with the same configuration options with no issue, but I want to make sure that this will not keep happening with future custom discounts. Has anyone ran into this issue before, or know what the root cause may be?

Thanks for your help!