I don't think the problem is with winrar.
At some time though you may wish to try 7zip (free)
Be sure to go into tools options and select all.
An example or rars is
If stuffpart4.rar is missing it will go through the motions until it cannot find the missing file and error out.
Some sites also have par files included with the rars. Pars will rebuild a corrupt rar.
A second advantage of pars is if you are downloading 75 huge rars........Get the smaller 7?pars...then skip a few of the huge rars. The pars will replace the missing rars.
Some sites still have fake ware. Looks legit until you try to unpack it.
I would google for the program you downloaded and try from another site.