The issue that I'm having is after creating a popnet flock animation, which is looking good but I can't find a way to make sure the mesh that is instances to these particles those not flip 360 around the velocity vector.

I've Found this previous post [www.sidefx.com] but is a bit old and wanted to ask if someone knew how to fix this.

Thanks in advance for the help.

Hello,
not sure if can help:
you could try to trace the trail of the particles with a Trail Sop and then, on the new curves, apply an "Orientation along curve" Sop to get smooth reference frames

What attributes do you have going into the sim? If there are no orient, N or up attribute, Houdini will orient using v. However, it has no way to determine the up vector and that's why you're getting flipping.

At the very least, give you source points N and up and this will probably fix it. You could post a hip file too.

Sean