For me, the solution was to manually change the "email body" page location as it appeared on the php page with my form. This location was being referenced in the PHP script at the very top of that form page. On my Universal Email 4 updated page, the line referencing the "email body" page location said "include("../WA_Universal_Email/WAUE_donate-securities_1.php");" (This was at about line 60 of the Webassist script which starts at the top of the page.)
All that needed to be done was to update that with the new location. For me, that was: include("../webassist/email/WAUE_donate_1.php");
I'm not sure if a later UE update will fix this or not; but for now, that's the work-around that solved my problem. Hopefully it helps you.
All the best!