It has been already confirmed that the hand is not an issue. Even Paddy admitted it and they took time to make sure. Kubica has been asked about the way he's holding the wheel in this interview:
https://www.bbc.com/sport/formula1/44086164
Today Robert said that it's the worst balance they had whole season and Lance had the same impression. As they were testing aero stuff, so they couldn't change anything with setup during entire FP1. Robert's (and Lance's) job in FP1 was to collect as much usable data as he can, so no fancy time attack driving for him today. Some voices suggested that bad baseline balance has not exactly been a coincidence, so in FP2 SS and Lance could manage a much better times with improved setup in FP2, to silence the critics regarding driver lineup. Well, Kubica is still the faster of the three, even though Lance improved by 1.3 s with new setup on FP2. With some more bad news, Paddy said that softer compounds simply wouldn't work today. On a brigher note, he and Smedley pointed out that they have pinpointed the source of aero instability. Same has been stated by RK, but sadly he added that it's not something that can be corrected within a day or a month.
Even though I'm really happy for Robert for doing a good job on his first official session in 7 years, there's not much more to be happy about, as it's an overall horrible weekend for Williams so far.