We use HelloSign a lot, and it is unreliable. Long waits for pages to load, and sometimes it cannot process a PDF that displays just fine in a variety of viewers. It just hangs with a message to the console every so often saying "Processing document". In our end to end tests Hellosign is often the part that fails, but that will work with enough retries.
I had such a poor experience that I briefly considered building a digital signature product because the bar appears to be pretty low between them and DocuSign.
Same experience, and it's actually quite unnerving for this to happen when you're doing something like signing equity grant letters and equally important documents where the effects of something not working won't be known for a long time.
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.
