Material Blueprint was reset automatically

Development Programming & Scripting Blueprint
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1

I have edited some material blueprint from the starter content and saved, but it always being reset to its original state while I open the UE browser.
I have no idea why it happened, have somebody met this problem?

2

For addition, I do this in UE5.1

3

Hey there @YosomiChann! Yes you’ve got it right, if you’re going to be working with anything from the starter content or engine, make a copy, and move it out to a different folder. Working on maps like Minimal_Default out of the box will fail to save each session.