I'm not able to share that scene but I am able to recreate the apparent memory leak in a simpler scene. In fact it looks like it has nothing to do with the variable mesh structure issue, it may be that there's a memory leak in any scene with a full scene reload when you render a frame sequence out do disk (using MPlay).
Attached is a simple scene where the RAM usage will grow every frame. Note that it's not leaking the whole context frame to frame so the allocated memory does drop moving to the next frame, but there's a net growth each time. It's significant enough that you don't need a particularly complex/heavy scene to run out of RAM in 100-200 frames or in the case of my heavier scene after about 35 frames.
Had to share via my Dropbox, for some reason whenever I try to upload an attachment the page just resets after I complete the CAPTCHAhttps://www.dropbox.com/transfer/cap_pi ... xclTuwhDys
Some notes on my system:
Plugin version: 2019.1.1.0
Octane API version: 2019.1
Houdini HDK version: 17.5.360
NVidia driver: 431.36