I've had several errors in kernel logs on device boot after all partitions were mounted.
ext3_free_blocks_sb: bit already cleared for block ######
After searching I've discovered that a bugfix for the same issue was already integrated in the kernel.
Then I've searched for similar commits on repository and didn't find anything so it seems like the bug was fixed on the mainstream and the issue is Android-related.
From the discussion on RedHat bugtracker about the bug I discovered that it can be reproduced with stress-test utility. Unfortunately, I don't know any of these for ext3
on Android.