I've found the cause of Jayce's Broken Animations
So you guys at Riot are probably tired of hearing this stuff from me about Jayce's animations and other assets not working (see: my boards / reddit post history), but I think I've finally discovered the cause of it the animations not working. Jayce's R passive.
While watching a replay of myself playing Jayce I skipped to a point in the timeline where I was farming in cannon form, without having my R passive up. I was shocked to see that my while auto attacking my cannon was actually using the proper animations that it should be using (expanding / contrasting on autos and shock blasts). To see if this falls in line with my theory that his R passive is the cause, I went back to the beginning of the replay, watching myself run to lane then farm from level 1 without having used my passive on anything yet. Sure enough, the animations are as they are playing a game on live (not working because of the passive being up). This also works in hammer stance as well, keeping animations working if you skip to a part in the replay timeline without Jayce's passive up. The attached link illustrates what I just described.
I know the team at Riot came to the decision that this was a trivial issue, but seeing that I've found the actual (PROBABLE) cause of this bug, would it be possible to re-look at this? To those who know of it's existence, I'm pretty sure they would like it fixed as much as I would, seeing how much better it makes him look. Thanks a bunch.
tl;dr - Switching stances on Jayce and having his R passive removes all of his hammer secondary animations (source - replays); see attached link.