Rick,

Great videos and yes you have "tail bobbing" pretty bad. Love the picture of you and your lovely young grand-daughter.

I've attached a couple pictues of the rotor head. As mentioned by ArrowNaugtic and Cx2cp+, try the lube first and give it a quick test flight. You should be able to move the flybar paddle, up and down, by hand, through it's whole range with no binding whatsoever.
If there is binding, you will have to back off the 5.5 mm (I'd try 1/8 of a turn, then retest) nut in the grip(see picture).Check all those tiny links on the rotor head and make sure none of them have popped off. If all that checks out, it may be due to a bent feathering shaft/spindle. I don't think weather was a culprint here, the other HBK2 flew great, and the kids in the background going down the street weren't all bundled up.

Dave / Choppersrule