Recent imports disappear unexpectedly

[chaosxian]

Once monthly I import credit card csv. After doing so, I categorize unknown category transactions, and add notes to key transactions. After doing all that I reconcile all new adds.

Then as an extra caution I "save as" the updated file to a new file name.

Today (a week later) I open MMEX and find that the last import and all its edits do not exist. Not only in the most recent file I did "save as" but the file prior to it.

This has happened several times in the past and is the reason I do the "save as". But now my strategy seems defeated. 

What am I doing wrong? Why has the most recent import along with all its changes vanished?

I'm still using 1.2.7, hesitant to go to 1.3 until I can understand what is happening with my work.

Thanks for your insights.