The fact that the same companies who make secure ATM machines can't apparently make secure voting machines suggest that these voting machines are defective by design.
/tinfoil
It's not the machines or the design that are the problem. It is human error. The whole process is a monumental task, and it is amazing it runs as smoothly as it does. Electronic voting did NOT create problems. It fixed some and added some. What it has resulted in in more focus on the process; making problems much more obvious and damning.
Most counties employ a handful of full-time employees.
Time tables are ridiculously tight. Every county is racing against the clock to proof and finalize all election materials (printed, mailed, and electronic). There never is enough time. Machines (mechanical or electronic) have to be prepped, tested, and shipped to polling sites. A small county in California has to prep more than 2000+ machines. This all happens within days or a short couple of weeks once everything is finalized.
Hundreds of volunteers need to be recruited, trained, and trusted to run equipment they are unfamiliar with. Equipment they will use and manage only on election day and only a couple of times every year (assuming the continue to volunteer).
Demographically the vast majority of these volunteers are retired, students, and out of work citizens. To put it plainly, these are not the most competent people to have running any form of voting equipment. They do not learn or adapt quickly. They all have individual personalities, and there is never enough highly trained staff to help/monitor these people in the field.
Election laws change several times a year. This means that no two elections are ever the same. So not only do you have to train new material, you have to untrain old material and old habits.. Again the demographics of your poll workers make this a monumental task. Most screw-ups on election day are the result of procedural errors or simple ignorance.
With regards to the machines...
Each election in each county is unique. All ballot information must be created in a publishing software package unique to a given county. In addition most counties have to create and proof ballots in multiple languages.
In many places (like California) a ballot rotation scheme is used based on congressional district. This is done to ensure the candidates are not in the same spot on every ballot. In my county this results in more than 500 unique ballot layouts that must be proofed and tested in the short time between finalizing the election material and election day.
Once the polls open it is up to the
trained volunteers to run, monitor, and secure all voting equipment and materials. It only takes a couple of machine failures/glitches and/or good faith mistakes by poll workers to completely fubar a precinct.
There are so many points of failure it really doesn't take much to create headlines.