One additional measurement you should take to nail this as a bad neutral connection is the voltage from L1 to L2.
When you see the imbalance between L1 / neutral and L2 / neutral see if L1 to L2 is also wandering. I expect it is fairly constant, and this nails it down as an unconnected neutral issue.
I had this in my house. We noticed it by our lights flashing when the load changed. I did not get good AC measurements as my meter took that day to go south. We have a friend at the local utility co and he got a tech out that day. Problem was at the power pole due to a fallen branch the year before.
When you see the imbalance between L1 / neutral and L2 / neutral see if L1 to L2 is also wandering. I expect it is fairly constant, and this nails it down as an unconnected neutral issue.
I had this in my house. We noticed it by our lights flashing when the load changed. I did not get good AC measurements as my meter took that day to go south. We have a friend at the local utility co and he got a tech out that day. Problem was at the power pole due to a fallen branch the year before.