Plugin conflicts with EDD (vendor registration issues)

Hi, I have a plugin conflict issue.
(In my website, “Ultimate Member” plugin conflicts with the Easy Digital Download’s “Frontend Submissions (FES)” plugin. )
I first submitted a support ticket to Easy Digital Downloads, but they said the issue appears to be on Ultimate Member’ side so I have to reach out to Ultimate Member.

“Frontend Submissions” plugin allows users to submit the registration to become a vendor, and after submitting vendor registration, “Vendor Application Pending” message should appear.
But the problem is.. After installing and activating “Ultimate Member”, “Application Pending” message no longer appears.
Instead, they are just remained at the vendor registration page and they can submit their vendor registration again and again… for numerous times.

When I deactivated the “Ultimate Member,” this problem was solved.
But I really need Ultimate Member for my website, so I don’t want to deactivate the plugin.

Is there anything I can do to solve this problem?
I’d really appreciate your help. Thanks.