My M2 said that he has memory full, after weeks of 75% full message. I did not have any new applications installed, and he just started not to work. I couldn't receive any messages, what's app was crushing time after time, and phone in general was completely useless. I reset the phone, and with not a single app downloaded it's 75% full again. I cannot update a single app because of that. Do you have any idea what the problem could be?