LumenRT 16.16.24.12 using RAM instead of GPU

Hi all,

Does anybody knows why the new LumenRT release is using RAM instead of GPU?

I have opened an 7GB .lrt file and hit play animation. My RAM went from 1GB to 47GB. The animation is glitching when playing because of the intense RAM usage.

The usage of GPU is 0%.

PC spec 

CPU : Intel core i7 8700k 3.7ghz

RAM: 64 GB 

GPU: 2 x Nvidia GeForce  GTX 1080 Ti

Does anybody has encounter something like this?

Or does anybody has a solution?

Many thanks in advance!