@zubozrout , @keneda,
I reinstalled UT, and the OS crashed another time.
This time the crash looks like I had run some other apps can write system partition while I using the tweak tool.
Then I reinstalled UT, and carefully used the tweak tool. But the OS crash the third time. The reason maybe I didnot use a password for my device while the tweak tool need a password.
And I reinstalled again. But yesterday , the OS crashed the fouth time! I justed picked a long touch on a link for open in another windows with a webber made app(That operation is very usual for a web browser), and the OS crashed.
It looks unusual operations will result conflicts on system partition. Also there is no approved or restart lomiri actions after editting with the tweak tool, that would make the system partition easily hurt.
In this days, the lomiri crahsed many times, most beacuse of the system is over load and the device be in hot. For this situation, I just reboot the device and it is ok.
That is my update information.

@tera ,thanks for your information.
I had sovled by parted tool.
I had resized the cahe and system size.
The device works well.
Many thanks.