Square wave inverter to LFP battery?

Some high end RV's come with a modified sine wave inverter installed....

I can only comment about things I have seen.

I have not played around with pure sine wave.

But seven different modified sine wave inverters reverted to square wave after battery voltage sags to a critically low level. Trace, Xantrex, and others did it. Forty years ago the instantaneous burn out of an electric blanket control taught me to be careful with asymmetrical wave form power.

Inductors heated up and caused FET transistors to draw additional amperage. Electrical motors ran hotter. Batteries discharged significantly faster.

;) your mileage may vary

Get rid of that and get a pure sign wave before you wreck things haha. seriously though a MSW can use up to 30% more power to run the same equipment due to inefficiency and noisy wave form. They produce more electrical interference and can damage sensitive electronics (read BMS) and anything with AC motors.

for the price difference nowadays there is no real reason to have a modified sign way anymore.

There are other issues with MSW inverters as well.. The biggest is that the "Sqauarish" waves have harmonics that can go all the way up into "Frequencies of interest) (TV/Radio) and cause interference with same.... PSW/TSW are far less likely to do that.

My psw inverters ... Well some very sensitive radios I have could not hear them at all MSW.... The Radio sounds rather nasty. (Radio is running on battery power)

MSW inverters are known to damage some electronics. Apple devices, electric blankets, and gas ranges to name a few. If you haven't burned up anything yet yoh're lucky.
MSW inverters are like black amd white TV's. Yeah, they work, but is anybody really that cheap?

Almot,

I did run my roof air and microwave with a modified sine wave inverter from Cobra. It was designed to work with motors.

I got a true sine wave as soon as I could afford it.

One reason I did so was the kill-a-watt would read the ac output voltage as 176.

In short, I think modified is a bad idea.

Square wave produces a number of higher frequency transient voltages which can cause the type of issues you're seeing. With your years of use I don't see a problem.

Sine wave inverters are cheaper these days and you may get longer life with some equipment.