Some ideas you may want to look into. In the drive there is an EEPROM chip...I think it's the U15 chip, that checks and validates programmed data after each run as it cycles the safety system. The chip is cheap but you may need the service tool to load any missing parameters. Not the easiest route. I doubt it's a door lock problem as those are easy to find. May be an issue with pre brake pick where the brake lifts before the doors close. This happens even if the doors reopen to allow more people in and can cause just enough roll back to create a fault. That's something that can be disabled using...you guessed it...the service tool. You can't even calibrate the load weighing system without it. Would need to see fault codes to really trouble shoot it. At any rate without the tool you may not be able to effectively fix and maintain it or perform annual and full load tests. It may be worth the investment if you plan to take other units like this one onto contract.
