Hi @Anonymous,
Could you please share a bit more about your scenario?
Do you put lot of questions of one record (of your SP list) into multiple Edit forms within different screens?
I have made a test on my side and don't have the issue that you mentioned. The screenshot as below:
In addition, I don't think the SubmitForm function could achieve your needs. If you use SubmitForm function to submit data into your SP list, it would add a new record into your SP list when running this function each time.
In other words, when you run the SubmitForm function within your first Edit screen, it would add a new record into your SP list. When you run tlhe SubmitForm function within your second Edit screen, it would add another new record into your SP list rather than update the record the first SubmitForm function created.
As an alternative solution, please take a try to achieve your needs using Patch function. I have made a test on my side, please take a try with the following workaround (I assume that you have two Edit screens within your app😞

Set the OnSelect property of the "Navigate" button wirthin the first Edit screen (EditScreen1) to following formula;
Navigate(Screen2,ScreenTransition.None)
Set the OnSelect property of the "Submit" button within the second Edit screen (EditScrren2) to following formula:
Patch(
'20180712_case4',
Defaults('20180712_case4'),
Form1.Updates,
Form2.Updates
)
Note: The Form1 represents the Edit form control within the first Edit screen, the Form2 represents the Edit form control within the second Edit screen.
Please also check if the following thread would help in your scenario:
https://powerusers.microsoft.com/t5/General-Discussion/Multiple-form-submit-tried-patching-and-submit/td-p/75581
Best regards,
Kris