DynamicForms + Authorize.net Sometimes Infrequently Duplicating Charges

We are troubleshooting a site where we have the following elements in play:
- DNN 9x
- DataSprings Dynamic Form
- this form is connected to authorize.net and is taking donation submissions

On occasion, not with every submission, but with perhaps 2 out of 100 in a month, the donation shows in authorize.net records has having been charged/made twice. In those circumstances, it is not two transactions within the same second, the second transaction might be 3 to 15 minutes after the first transaction. In one case, the second transaction was an hour or more later.

Within the Dynamic Form module, we have it set with some protections such as cookie settings that don't let a person submit the same module/form a second time... they are blocked from hitting submit a second time if they come back to the page, or if they click "back" and reload the same form, it doesn't let you submit it again a second time. We've tried a few ways to attempt to load again the same form including duplicating the tab... double clicking on the initial submit button... and a few more ideas.

Has anyone experienced a similar type of duplication submission issue? or perhaps an Authorize.net issue?