Items not saving to current time

Hi users,

I'm having an issue with items not saving to the current time.  This happens for parts, assemblies and drawings where I will save the work but it doesn't update the time in explorer, and stays at the previously created time.  Sometimes when I go to re-open it's either updated the model and kept the old time, or actually not saved work at all.  So my safeguard it to 'save as' with 1 digit difference as a backup, but obviously this is not sustainable.  

It's actually happened in the past and seemed to fix itself so I forgot about it, but now I'm wondering have any users experienced this before?