The OP lists his occupation as retired. I read his post twice and was going to reply with the usual comments.
Secondary actual voltage, load, lowest secondary voltage with 'heavy load'. Actual voltage at apt panel; etc.
I stayed silent on this
As you know the 240 volt items are AC, maybe cooling, maybe water heater. They tolerate <240 volts
I have not heard of any issues from the +/- 600 apt units that have been built in the last 2 years.