Niagara System user paramemters will reset upon restarting if they are used in a Blueprint. This also occurs to the system if you move the blueprint after making changes then pressing Ctrl+Z. 

Found in 4.20 CL# 4369336, 4.21 CL# 4613538, 4.22 CL# 4751672

Steps to Reproduce
  1. Open the Editor
  2. Enable Niagara and restart the editor
  3. Create a basic Niagara Emitter with a user parameter for spawn rate. 
  4. Create a Niagara System using the emitter
  5. In an Actor Blueprint add a Niagara Component and set it to the created System
  6. Set the user parameter to any number other than 0 and compile/save the Actor
  7. Place the Actor in the scene, select the Niagara Component and change the user parameter
  8. Save and close the project
  9. Reopen the project

Steps with attached project:

  1. Open the project
  2. Place BP_BuggyExampleBP in the scene
  3. Select the Niagara Component and change the User.SpawnRate parameter
  4. Save and close the project
  5. Reopen the project

The user parameters will reset back to what they previously were

The user parameters would not change

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ComponentRendering - Niagara
Affects Versions4.204.214.22
CreatedJan 18, 2019
UpdatedMay 1, 2019