Error saving the sheetnod

Hello

I edited a sheetnode to put new content on it and when I try to save it I had an error and I loose all the new content that I wrote on it. I'll put a screenshot where appears the error that it gave to me. It happens to me a lot of times and the strange thing is that when I edit it and put new content little by little, saving each time I put a bit it makes me well but If I put it all and try to save it gives me the error and I loose everything I edit.

Thanks for the help