So some of these are bugs, some of these are by design.
Silencing Watchful Sentinels doesn't work
By design - you cannot dispel a Watchful Sentinel to prevent it flipping (think of it like Tribals). Watchful Sentinels are still Sentinels - so the only way to prevent them from flipping/transforming is by not triggering them, or killing them. You can however, dispel everything else off the token as normal.
Bouncing Sentinels (Sandswirl Reader, Hailstone Prison, etc)
I believe the intended effect here is to return the actual card (Freeblade, Mind-Cage Oni, etc), not the 3/3 token
I don't have a master list of bugs/intended interactions (I'm off today since it's the weekend) but we do plan on making some bug fixes in the nearby future.
Keep this list rolling guys, it's a great reference to see what needs explaining or fixing