On removing page number from Table of contents [removing #], the hyperlink goes away for second half length of the tab fill. Tab fill is the “…” which is only clickable for the first half of its length. version 6.4.5 on Linux.
I reproduce it here in a fresh document with LO 6.4.5.2. I had a look at the underlying XML without seeing anything unusual (like a wrongly closed element). IMHO, deleting the # marker without deleting the leader tab T is not a good formatting decision. The leader line ends on no information. My personal choice would be to remove it altogether, eliminating the problem simultaneously.
Nevertheless, there may me a bug in the rendering engine. Developer’s opinion is needed. Submit a bug to get authorised feedback.
From what I understand, your bug has been screened by the “triage” people and not rejected (good point). They’re asking their Quality Assurance guys to have a look at it. Unless they add a new comment in the bug report requesting more information from you, there is nothing to do for the moment.