My generator and washing machine

Hi everyone, I have a problem with my generator and my washing machine.

I have in Spain a 4KVA Diesel machine. I am not sure what the engine is but I feel sure it is made in China.

It works fine for eveything except the washing machine. To operate that, we have to switch on a fan heater as well and adjust the settings as the wash progrsses.

Any ideas what the problem might be would be appreciated

Sounds like the washing machine is not taking linear current and upsetting the generator,what does the washer do without the heater connected?

is the washer a newer one with a vfd instead of transmission? the generator might need a more constant load.