Help test bug - unintended skip ahead

Over in the thread Unintended Skip Ahead, a few of us have been trying to track down a bug when you are fastforwarding, and you suddenly find yourself further ahead in the program than you expected.

I have developed a set of instructions that demonstrate the bug. I'd like some help in narrowing down which portions of the instructions are not important.

1. Schedule a 4 hour block recording in Medium quality (I found that Educational Access has 4 hour blocks).
2. When 2 hours and 58 minutes have been recorded, begin watching the show from the start.
3. Hit the fastforward button twice; the current position indicator will start moving forward along the green bar.
4. Watch the right end of the green bar as it approaches the 3 hour tick mark.
5. When the end of the green bar hits the 3 hour tick mark, the current position indicator (the white line with the time above it) should suddenly leap ahead by about 8 minutes.

My stats:
Series 2 60 hour TiVo. (I recently replaced the A drive with a larger Weaknees unit, but I had the problem before the replacement as well.)
TiVo System 7.2.1. (I saw the problem in 7.2 and 7.1 as well. I've had the TiVo for a couple of years, and didn't see the jump on any previous system software.)
Cable input, no box.
Recording quality: medium. (I have also observed the problem in High.)
Recording length: at least 3 hours.
Watching "live behind the buffer".

It is possible that the recording length and quality don't matter, but that it is more likely to hit the magic moment when watching a sports event, as there are more fast forwards and you are more likely to be watching as it records. It may be hardware specific.

Things to test:
1. Does it occur at 1x and 3x fast forward speeds?
2. Does it occur on all hardware that has at least System 7.1?
3. Does it occur at every tick mark?
4. Is there a minimum recording length for this to occur?
5. Is there some other criterion that I missed?

Please help.