Problems with the population. (Cities: Skylines)

I reached the 100,000 mark and then there were problems. The population began to disappear all the time. For example: 160, 100, -130, -40, 60, and so on.
I don't know why this is going to happen. Happiness rates about 90, health 80, noise does not bother anyone. What could be the reason for this?
Also, I have some incomprehensible anomalies with income. It rises for a while and even reaches 155 thousand, but then quite abruptly goes down and sometimes even goes to the bottom, and then again up and so back and forth constantly.