partial file saved with large file modification

[ydzdfci]

I have an xml file about 6G+, it takes about 30 seconds to open and after I modify one line and save, the new file size decreased to 2G+. Most lines are lost.
I don’t have XML Tool installed

It happened in both versions (Notepad+= v8.3.3 64bit, v8.4 64bit)
Windows 10 pro
Plugins:
AutoSave 1.6.1
Code Alignment 14.1.107
Compare 2.0.2
Explorer 1.9.5
Mime tools 2.7
Npp Converter 4.4
NppExport 0.4
Snippets 1.7

[Alan Kilborn]

@ydzdfci

Perhaps best to try the operation sequence again with NO plugins at all?