Is this normal?

Nope :-)

As with choroba, even with the DTD, it works for me.

as I do not have any TBXcoreStructV02.dtd, how can I jump this line? As the XML is huge, I do not want to manipulate it.

Well, you could add load_ext_dtd=>0 to the XML::LibXML::Reader constructor, but that's really just a workaround, and I can't even say if it'll help fix your crashes. The better solutions would be to either obtain the right file(s), and fix the crashes overall, such as by trying to upgrade your libraries.

BTW, since you just added that in a third edit to your node, please see How do I change/delete my post? to avoid confusion.