RPI3 USB SSD missing folders after reboot

Hi I am having some issues wih USB installation, I tried different times and all of them resulted in the missing folders (DietPi is the easiest to find, but I also lost a docker installation) sooner or later.
Two or three times I just installed plain dietpi (DietPi_v6.25_RPi-ARMv6-Buster.img) and when asked to install the additional softwares I only choose to replace dropbear with OpenSSH then rebooted and at the next login the dietpi folder was empty , nothing on var/log folder, /boot is filled with .rec files. Other times it reboots fine the first time but I get the same problem after the second or third reboot (shutdown too creates the same issue). I tried a second SSD but same problem. I installed the same image a month ago for testing other softwares and it worked flawlessly, the problem began after I flashed the same dietpi image, so my guess is there is something wrong with the latetest updates.