www.makemkv.com

Been recently backing up DVD to my computer and I notice on every few disk I get these three lines
Calculated BUP offset for VTS #1 does not match one in IFO header.
Calculated BUP offset for VTS #2 does not match one in IFO header.
Calculated BUP offset for VTS #3 does not match one in IFO header.
Although As far I can tell the backup seem fine due I need to worry about these errors?

I've seen those messages for years and they have caused no problems for me.

DVDs are not always authored with care and you sometimes see strange errors.