The same thing happened to me, a network file finished one day, the next day the file was different and had the wrong recording time. I know that the changes were saved correctly because the .bak file with the corrections made was in the same location and with the correct saving time.(wich allowed me to recover my changes)
Could it be related to the way Windows saves files? Can another PC, previously disconnected from the network, revert de files to the previous state when connecting at a later time ?
I had a similar problem with an external drive and discovered that the problem was related to the way Windows shuts down (or doesn't actually) and how USB devices are disconnected. What I discovered was that when "turning off" the PC (let's call it the 1st PC) with the external disk connected, depending on the shutdown and USB settings, Windows takes a photograph of the disk structure. If I remove the disk and make changes to the files on a 2nd PC, reconnect the disk to the 1st PC, when I connect it the disk appears to be unchanged by the 2nd PC. The conclusion I reached was that Windows thinks that the disk was never disconnected from the first PC, and as when recording files the empty space on the disk is used, the previous version is still there to increase the confusion.
I already managed to solve it with external USB disks, with files on the network I don't see how to solve it.