@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.

@lgtrombetta , mine is Meizu MX4. I went to the housetop of a building, open the uNav. Then the GPS works.

I used UT tweak tool to try the desktop mode.
After a little test with desktop mode, I changed back to mobile mode.
Then the OS crashed.
If each time of mode changed, should reboot the device?
I found double changes with tweak tool, only the first click works.
So I had to reinstall ubuntu touch. That's very trouble because of poor web speed.

My device: MEIZU mx4

@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.

error information:
Error: adb:push: Error: {"error":{"code":1},"stdout":"adb: error: failed to copy 'C:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\ubports-a95fdf05c877099caaabe104ff9b7b1a848ee4868b74c23f1f13232b58d9085d.tar.xz' to '/cache/recovery/ubports-a95fdf05c877099caaabe104ff9b7b1a848ee4868b74c23f1f13232b58d9085d.tar.xz': remote No space left on device\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\ubports-a95fdf05c877099caaabe104ff9b7b1a848ee4868b74c23f1f13232b58d9085d.tar.xz: 1 file pushed, 0 skipped. 1.7 MB/s (368184352 bytes in 212.294s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\ubports-a95fdf05c877099caaabe104ff9b7b1a848ee4868b74c23f1f13232b58d9085d.tar.xz.asc: 1 file pushed, 0 skipped. 0.6 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\device-83fddedbd574169d9ccf1d55ab25c8b3956062e71e693cd8a23c32e2cdd4d48a.tar.xz: 1 file pushed, 0 skipped. 2.1 MB/s (110714872 bytes in 51.100s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\device-83fddedbd574169d9ccf1d55ab25c8b3956062e71e693cd8a23c32e2cdd4d48a.tar.xz.asc: 1 file pushed, 0 skipped. 0.5 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\keyring-28992f008be20d562ea06745f563d3abe00b08da1b16e5b92e448e2d4ba21e9f.tar.xz: 1 file pushed, 0 skipped. 1.2 MB/s (1564 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\keyring-28992f008be20d562ea06745f563d3abe00b08da1b16e5b92e448e2d4ba21e9f.tar.xz.asc: 1 file pushed, 0 skipped. 0.3 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\version-15.tar.xz: 1 file pushed, 0 skipped. 0.4 MB/s (468 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\version-15.tar.xz.asc: 1 file pushed, 0 skipped. 0.4 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\image-signing.tar.xz: 1 file pushed, 0 skipped. 1.1 MB/s (940 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\image-signing.tar.xz.asc: 1 file pushed, 0 skipped. 0.5 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\image-master.tar.xz: 1 file pushed, 0 skipped. 1.0 MB/s (900 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\image-master.tar.xz.asc: 1 file pushed, 0 skipped. 0.5 MB/s (488 bytes in 0.001s)\r\nC:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\ubuntu_command: 1 file pushed, 0 skipped. 0.8 MB/s (716 bytes in 0.001s)\r\nadb: error: failed to copy 'C:\Users\abixz\AppData\Roaming\ubports\arale\Ubuntu Touch\device-83fddedbd574169d9ccf1d55ab25c8b3956062e71e693cd8a23c32e2cdd4d48a.tar.xz' to '/cache/recovery/device-83fddedbd574169d9ccf1d55ab25c8b3956062e71e693cd8a23c32e2cdd4d48a.tar.xz': remote No space left on device\r\n13 files pushed, 0 skipped. 1.7 MB/s (478906740 bytes in 266.478s)"}

At the last step, the installer cannot push the ubports 16.04 files to MX4. The device is unlocked, booted, and sucessfully installed ubports 15.04 by TWRP. Please help me.