If OEBPS/Text/ is
exactly what's reported in the "File" column of Flight Crew's validation check window, then search for
Code:
href="../Text/#[^>]*"
in all html files (regex search-mode).
That will basically look for any url fragments without a file name, which is commonly the cause of that particular error.
Could also be something similar in the toc.ncx file but that would likely generate an additional error as well. You could search the ncx file just to be sure:
(also regex search-mode)
It's also remotely possible it's just a simple typo and you'd want to search for:
in all html files. It's not very likely, but it
would generate the error you're reporting.