Confluence intermittently displays #contentlink2 ($P false false) while uploading/installing/updating/enabling plugin

Issue Summary

This is reproducible on Data Center: (yes)

Steps to Reproduce

1. Download a plugin installation file (preferably larger than 40 MB)
2. Navigate to Manage Apps (tab A)
3. Open a new browser tab for the Confluence Homepage (tab B)
4. Upload app (tab A)
   • In our case, we have used draw.io Diagrams & Whiteboards, and Gliffy Diagrams for Confluence to reproduce the behavior. 
      
5. While uploading/installing the plugin, switch to tab B and refresh the page (Ctrl + Shift + R   - Reload the current page, ignoring cached content) multiple times 
6. Once the installation is done, check the sidebar, login page, etc

Expected Results

The sidebar should display the page titles

Actual Results

Sidebar:

Login:

Global Permission: 

Workaround

Disabling/Enabling the plugin 

Clear Confluence plugins cache