We've found this as well. So much so that a plan is in place to move providers soon. It often just fails for no good reason at all. During testing I found that

We've found this as well. So much so that a plan is in place to move providers soon. It often just fails for no good reason at all. During testing I found that the UI completely breaks when a signature is below a certain size. I reported this, but still seems to be a problem.