BR7070 new to me

I purchased a 2010 BR7070 twine auto wrap recently. The previous owner said that they baled 3500 bales with it. I have baled my first 35 bales now I have some questions

1. Left side bale size sensor is not visible on the auto wrap monitor. I checked the sensor and it is clean and not blocked by hay. Right side works great. So far my bales look great, except for the first 5 bales I did. Any ideas to test the electrical side of the sensor?

2. When I drive straight everything works great, but any slight turn the vibration from the pto shake my tractor enough that I’m worried my pto will break. Could this be a pto shaft that is not true or straight? Should I replace the shaft?

3. Rear door lock does not move to the locked position. I try to move it up put it won’t go high enough to move over to locked. Any ideas here?

4. How to you fix an issue when the idiot (me) baling accidentally opens the rear before the bale is completed and before the twine has been engaged? I found out closing it and continuing to bale is not a good idea.

Thank you for your responses. I do enjoy reading all of comments on other posts. Moving from a NH 316 to a BR7070 is a big jump for me. Any help would be appreciated. -Todd

Edited for typos

BR7070 new to me