Macbook login - wrong password but it is correct for sure

Hi,

it's the second time I've got crazy experience with login to my Macbook. This morning, I tried to clean my keyboard and as a result computer turned on few times, also incorrect, random passwords was entered few times. After cleaning, I tried to log in with my normal password.

AND it was INCORRECT! Also, there's no chance it was changed by mistake!! I had to reset the password, thankfully there was option to do it. Last time, there was not such an option and I had to reset my whole computer!! Even on hotline the consultant was shocked with such a lack.

Now I'm worried that some day I will lose all my data due to such a stupid mistake!

How is it even possible?