Wow, 12 months and no other responses? Starting to become a little disappointed with UM. There's a lot of little things that, for a membership plugin with forms, you would expect to work better.

For example (and to hopefully answer your questions), what I have noticed is that if if there is a missing required field, or bad data in a field that the form won't accept, instead of scrolling automatically up to those errors (which I feel is pretty standard function for forms!) it just sits on the bottom of the form where you hit "save" or "submit", effectively looking like it just isn't saving. Wish the UM devs would chime in!