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 with attached project:
The user parameters will reset back to what they previously were
The user parameters would not change
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-68722 in the post.