The jerkiness has been happening since the implementation of the stroke play game (or at least since I started playing it).
It tends to happen more frequently in multi player games, but it also happens in solo play. Time of day doesn't seem to make any difference as the problem is seemingly random in nature. I've had games where the swing meter was fine for the first couple of holes, but then out of the blue it gets choppy (or worse, freezes), and then it doesn't happen again in the game. I've had games where it started out bad, and never gets better.
The only program running at the time is WGT in Chrome (which I found to be a better browser for this game). I run an extremely streamlined WinXP. Anti-Virus is disabled and I only have a software firewall running at the time (which has no effect on the game). I have around 23 processes running, and besides the firewall and disabled anti-virus, every process is a Windows process (no other non-Windows processes are running).
It doesn't happen all the time for me, but it strikes at very inopportune times (such as when I'm just about to click for accuracy). I've had way too many games where my click isn't registered until a second or two after I clicked, resulting in badly missed shots. Considering this game revolves around the swing meter, any inconsistencies in the swing meter is problematic and should be seen as priority in getting fixed, IMO.