UserAgent: Mozilla/5.0 (X11; CrOS x86_64 11021.56.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.76 Safari/537.36
Platform: 11021.56.0 (Official Build) stable-channel cave

Steps to reproduce the problem:
1. Connect the Bluetooth control device (Bluetooth mouse)
2. Disconnect the Bluetooth control device
3. Now disconnect the device from the keyboard dock or
Switch to tablet mode

What is the expected behavior?
Bluetooth is disconnected and in tablet mode
Screen rotation should work normally when you enter.
+ Device remains stuck in desktop mode after disconnecting Bluetooth mouse. Expected behavior is to return to tablet mode.
+ Device is forced into landscape orientation when connected to Bluetooth mouse. Expected behavior is to allow portrait mode for various use cases. Essentially, the software appears incapable of distinguishing between "true" docked, desktop mode and desktop mode via Bluetooth mouse & keyboard. Needless to say, it should be able to do so.(hp x2 chromebook)

What went wrong?
First of all, this is quite a complaint to users
I want you to know that it is an old nightmare bug.
The problem is not only hp x2, but also pixel books and asus c302
Flip or occur on all 2in1 devices with keyboard dock present
When connecting a Logitech mouse with a usb wireless receiver
You can still use the mouse after switching to tablet mode.
It also works when the screen rotation is connected or disconnected.

But according to the user reports
Bluetooth control devices such as Bluetooth pen or mouse
If you only once connected.
How to rotate the screen in tablet mode
It can not be resolved except on reboot.
This proves that chrome os is an incompetent os that can not use a Bluetooth mouse.
A bug fix is a serious issue that needs to be released to the stable version right now
There are many users who do not like to write Chromebooks because of this issue.
It's already been reported as a duplicate issue.
I'm reporting this again because it's still not fixed.
Whatever Chrome version 68 to 71
There is nothing different. I would be very satisfied with the Chromebook if it was not just this bug
I am under a lot of stress from this problem.
chrome: // flags / # force-tablet-mode
When the mode is changed
  It is forced into tablet mode, but you can still use a Bluetooth mouse
The screen rotates well. This proves that there is no problem with the device
There are very many users who have this problem
I would like you to know the developers.
(Written by Google Translator)

Did this work before? No 

Chrome version: 70.0.3538.76  Channel: stable
OS Version: 11021.56.0
Flash Version: 

https://bugs.chromium.org/p/chromium/issues/detail?id=882410
https://bugs.chromium.org/p/chromium/issues/detail?id=863149
There are many other bug reports, but I'll skip it.
The Chrome Help Center does not allow you to reboot and answer that it is a bug.