I2C group changes to root

I had this issue couple times when on boot i2c interface changes group to root automatically (with date 01/01/1970), not sure what is the cause of this problem but it goes out after rebooting. This causes IOError: [Errno 13] Permission denied when I try to use it with python as it is not in i2c group. Has anybody seen it before and knows how to prevent it happening again?

$ ls -l /dev/i2c*
crw------- 1 root root 89,  0 Jan  1  1970 /dev/i2c-0
crw-rw---- 1 root i2c  89,  1 Sep  1 08:37 /dev/i2c-1
crw-rw---- 1 root i2c  89, 10 Sep  1 08:37 /dev/i2c-10
crw-rw---- 1 root i2c  89, 11 Sep  1 08:37 /dev/i2c-11
crw-rw---- 1 root i2c  89, 12 Sep  1 08:37 /dev/i2c-12
crw------- 1 root root 89,  2 Jan  1  1970 /dev/i2c-2
crw------- 1 root root 89,  3 Jan  1  1970 /dev/i2c-3
crw-rw---- 1 root i2c  89,  4 Sep  1 08:37 /dev/i2c-4
crw------- 1 root root 89,  5 Jan  1  1970 /dev/i2c-5
crw------- 1 root root 89,  6 Jan  1  1970 /dev/i2c-6
crw-rw---- 1 root i2c  89,  7 Sep  1 08:37 /dev/i2c-7
crw------- 1 root root 89,  8 Jan  1  1970 /dev/i2c-8
crw------- 1 root root 89,  9 Jan  1  1970 /dev/i2c-9

Could it cause by the time lost by remove the power?

Interesting comment, what I found is this issue required internet connection to correct itself

May need to monitor it to figure out if the root cause is time lost because power remove. And yes it network connect it will correct the time after Network up, but don’t know the I2C group changed before or after the time sync up with time server.

Any idea why this requires clock sync?

Sorry, I am not sure the root cause just suspect the if the time lost cause the problem.