Read Errors - Direct BD Rip vs Rip From ISO

[SkyLiner]

When I rip a BD to ISO using only AnyDVDHD...and get NO read errors during the process; I sometimes get read errors when I re-rip said ISO to a new ISO using CloneBD (to select only desired Titles). The 2 times I've had this happen (with "2012" and "Jackie"), even though I get a couple read errors during the process (of creating the new ISO from the original 1:1 ISO), CloneBD forges through and continues creating the new ISO to completion. The reason I find this interesting is because when I run into a BD that gives read errors when trying to create an ISO (either by using only AnyDVD or by using AnyDVD in the background and CloneBD to create the ISO), the ISO creation process stops and doesn't let me complete. But on these 2 titles I mentioned, I get no read errors during the initial ISO creation process, but I do get the read errors (albeit not enough to stop the process) when creating the second ISO. You would think that if there were errors on the BD, they would have showed themselves during the initial ISO creation and not during the 2nd creation of the ISO from the original ISO.

Any thoughts?