I'm trying to salvage what I can from an HDD that malfunctioned. I'm still not sure it's a hardware issue, but I'm trying to find out. When doing a deep scan Recuva hangs indefinitely at 1% of phase 1 (411133 files found). The problem might be it hit a bad sector and can't go forward. Is there any way to force Recuva to skip that sector and move on?
No. Bad sector remapping should be handled by the disk controller, but I guess that's part of the definition of malfunctioned. I would first try running a normal scan with show undeleted files checked. It's fast so you might as well have a go, and you are trying to recover live files, aren't you?
As for the deep scan I can't suggest much more than running a chkdsk, which shouldn't affect live files. However the state of the disk might result in some lost data. Even if a deep scan finished it will only show deleted files, unless you do as above, so you might as well just run the normal scan.