How does Merge work when Importing and Exporting from Google Sheets?

Hello,

First off, thanks for this amazing asset. I am using the Google Sheets integration and wanted to know how merging works. Whenever I want to synchronize my language source with the I2Loc sheet, I first do Import > Merge, and then Export > Replace. But I found certain translations get unset when I do this. Any idea why this might be happening?

Percy