I use extensively Webform Integration to register Memberships.
Since mid April (precisely April 21st, but I don't remember when I did some Module Updates), memberships have not been recorded anymore, though no error message is displayed and Webform Mails are sent (and received).
Some information before further investigation :
- My memberships have no associated Contribution and are for Life
- They have some associated multi-valued Custom Fields
- When they contain a new Contact, the new Contact is not created either
- I have the same problem on a Test Civi 5.0.0 configuration
I will report this as a bug to https://www.drupal.org/node/add/project-issue/webform_civicrm, and keep this informed if I find other informations.