The fact that you, who know all the easy fixes, were stumped with this one indicates that this is a topic which deserves systematic scientific study. You have learned that you are too good with this stuff to be an adequate test of whether the technology you want to use is consumer-ready for your market. You need to get something like this checked out by less expert users before you decide it's usable enough. You have learned that web forms are not being used because they are easy for the user. They are being used because they are easy for the server.
Most users can cope, so the server gets away with it.
You got caught because you actually care about the users who fall outside that group that can cope. You have seen the results of this difference in the statistics of your user results. Thank you for sharing this tale with us. It is an important calibration of just where we are on forms accessibility. Maybe with this evidence we can get something effective done about it.