Your material doesn't look like it's displaying correctly to me in the channel box.
in zMaterial2 I don't see rest-scale, pressure or surface-tension
in zMaterial3 I don't see surface-tension
On the zTissue node I don't see any of the corresponding envelope attributes.
In the Ziva 1.4 release notes:
There is a MEL script to unhide the new attributes if you're opening scenes created in 1.3 and earlier (they were always there, just hidden and non-functional)
select `ls -type zMaterial`
setAttr .restScale -channelBox true
setAttr .pressure -channelBox true
It's important to ramp on these values over time at the start of your animation. This could be the reason your collisions are getting missed there on the front leg.