Phil. Do you think you could have just inadvertently changed the ordering sequence?
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Can you set a somewhat more meaningful file name pattern, like [DATE][TIME]XYZ... on that camera?
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See this link for what I mean:
https://www.youtube.com/watch?v=Tj23RLnR5WI
and the user manual on P 228: File/Folder Settings.
The last will tell you what's set now.