I don't use Macrium (still with Ghost 15) but that's not a flaw with Macrium. To me, anyway.
It's caused either by a change in the VSS snapshot, which is taken taken before imaging begins, or possibly by write caching not being enabled on your external HDD.
That info is garnered by google.
I don't see where Macrium is really at fault, though a case could be made for that. Ghost 15 isn't perfect either. OTOH, maybe software should be perfect. We can dream.
To my mind, a real failure is when the image won't restore properly.
Do you image cold, using the "rescue environment?"
I've never done it any other way, except when I was playing with the inbuilt Win 7 imaging.
Not saying that should be accepted practice, just my preference.