Hello everyone 
I’m running into an engine limitation regarding morph target additive animations setups.
There is currently no way to clamp morph target values on a mesh, resulting in values shotting above 1.0 in additive animation setups.
Here is a rough visualisation:
Even though this is not a perfect solution for every scenario, there is hardly any situation where you would actually want your morph targets to shoot over 1.0, and allowing clamping for morph target values (either as an option on the mesh or for each individual morph target) would be a good failsafe and allow for more modular facial animation setups.
Let me know if you need me to clarify anything!
Thank you for your time