Issue Description：
When the browser fails during the upgrade, the following symptoms may occur:
- The browser closes unexpectedly.
- The browser does not respond for a long time.
- The interface of the browser cannot be maximized after being minimized.
- The white screen error occurs on the browser unexpectedly.
- The browser closes abnormally during the upgrade. If you re-login, the upgrade progress is invisible, and the upgrade or rollback control page cannot be opened.
- After the upgrade or rollback, if you click Rollback or Upgrade on the left part of the page, the system displays a message stating that the operation is not allowed.
Possbile reason：
The CPU usage by the browser is excessively high.
Solution :
1. Close the browser, and then exit the upgrade tool.
2. Clear the buffer of the browser.
3. Wait for seven minutes, log in to the upgrade tool again, and then check whether the previous upgrade task is displayed.
Yes: No further action is required.
No: Go to 4.
4. Use the Information Collection Tool to collect items in Common Fault Analysis Scenario.
5. Contact Huawei technical support engineers to rectify the fault.
