[oldE]

For years when the power went out we had an old Coleman generator which would supply enough juice to run our fridge and freezer or other small appliances as needed. A few years ago, we upgraded to a larger generator which is wired in through a breaker panel. It handles the essential loads such as water heater,lights, pump and about half of the electrical outlets . It is a great bit of peace of mind, as we can live almost normally if there are major power outages.
There is one issue, however: the freezer doesn't like the generator supply. It will beep periodically, try to start and usually shut down within a second. Also, our washing machine won't complete a cycle if powered by the generator.
I have a theory the old generator (30 years old) produced a natural sine wave which the electronic brains of the freezer and washing machine needed, but the electrical output of the new generator is a "squared off wave" which doesn't seem to bother our fridge or even our computer but upsets the control modules of two appliances.
Might my theory be valid? If so, is there a cure, aside from changing the generator or the freezer and washing machine?
Any advice or suggestions appreciated.
Best
Les