See
https://github.com/wmde/fundraising/issues/1083
https://github.com/wmde/fundraising/issues/1090
https://github.com/wmde/fundraising/issues/1091
Code changes for this feature have already been deployed to the production systems. In order to have it still working, temporary template changes were made to the following pages:
https://fundraising-cms.wikimedia.de/index.php?title=Web:Spendenseite-DefaultSkin/test/MembershipApplication&curid=106&diff=571&oldid=559
https://fundraising-cms.wikimedia.de/index.php?title=Web:Spendenseite-DefaultSkin/test/MembershipApplicationEmbedded&curid=109&diff=572&oldid=217
https://fundraising-cms.wikimedia.de/index.php?title=Web:Spendenseite-DefaultSkin/test/MembershipApplicationForm&curid=110&diff=573&oldid=564
The templates need to be adapted again to actually activate this feature.