Using Shuriken alpha values to control non-alpha values in shader

I'm working on a bubble shader to be used with Shuriken. Apologies if what I'm trying to do seems dumb.

I'm using vertex colour alpha to change the speed of a panning texture that distorts the bubble's UV's so it can be controlled/affected by alpha set in Shuriken. Higher alpha levels increases the speed of the panner making the bubbles wobble faster.





Alpha set in Shuriken that isn't changed during the life of the particles is fine eg. Start Color. I can set random between two colours and set different alpha values and the bubbles wobble at different speeds. It's great.

But alpha that changes over the life of the particle gives undesirable results eg. Color over Lifetime, Color by Speed. These make the panner glitch and pop constantly.

My question is if this is a bug with Shaderforge or Shuriken, or am I doing something wrong/silly.

Cheers