Different file sizes in multi-channel recording

I used Cubase LE AI Elements Ver 8 to make some 48khz, 32-bit multi-channel recordings.
I had a 4-ch Ambiphonics mic, 4 channels of Sennhauser mics, and 3 Shure mics.
I recorded over 50 sessions and found a peculiar issue in four of them.
One or two of the 10 file sizes were different.
Examination showed that in 3 instances a small bit (2 to 10 seconds out of 20 minutes total) was missing from the file beginning compared to the other files.
In one instance there was also a small initial bit missing but other missing bits in the middle of the file.

Is it possible that these errors came from Cubase file storage code?
I can’t imagine how mics could do this.
Also the PC is state of the art, big and fast and no PC file system errors were reported.
Any ideas?