You are correct in thinking that that model should be able to playback Hi8 and Video8 tapes.
If you haven't already, download the manual direct from Sony
here.
In it you will see that there is a "PB" setting that will force the camcorder into analog play mode.
However, Hi8 and Video8 playback in a D8 camcorder (the ones that can do it - some cannot at all) can be problematic. This was also discussed in a thread on this forum
here.
BAs you suggest, the problem could be worsened if that the tape is LP, not SP, but I suspect it is not. "120" tapes record 2 hrs in Hi8 and Video8 formats. They record 60 min max. in a D8 camcorder because the tape speed it doubled for digital recordings.
For playback, the D8 camcorder has to sense whether the tape is digital or analog and switch to the proper tape speed, head speed and processing. I assume it defaults to digital so if it can't track/read a particular analog tape quite well enough, it never knows to change modes. I have both a Sony D8 and a Hi8 model. The D8 always misses a few frames at the start of a new section as it tries to determine the format.
Have you played any other tapes in the 460? Have you tried to record anything with it on a fresh tape? I would try that before I cleaned the heads. But dirty heads could definitely be the problem.
But this may just be a case where that specific tape won't play in that specific D8 camcorder. This appears to be a risk when using a D8 for analog playback.
BW