Pokemon UltraSun weird in-game issue

I don’t know if this is a common issue or if it has to do with the emulator itself but I often get pokemon with the same nature, at first I thought it was a coincidence but It happened again and again, not always but still noticeable, in fact all pokemon in my team has the same nature, I have played only for a couple of hours and I don’t have a pokemon with the Synchronize ability (increase chance of having the same Nature)

Do you always play at the same time? Is your ROM modified? Need more info.