You run into an internal problem.
Many people were working trying to fix that bug.
Can remember that Brov was fixing some variable from
mp_variable to
mo_variable for better downloading
but the 99% bug was never able to be fixed.
There are to less good programmers working on that project
-----------------------------
From experience:
After some while, you'ved restarted, set your download to <Pause>, wait some while ( 2 or 10 min ) then rightclick the download and choose <resume>
That's the only hint.