chained lerps for displacementmaps break tesselation on landscape

finally found the core of my problem:
im using too many lerps to generate my displacement for my landscape material.
here is what i have:

disp0030a lerps with disp0030b via noisemap → result disp0030

disp3060a lerps with disp3060b via noisemap → result disp3060

disp6090a lerps with disp6090b via noisemap → result disp6090

disp0030 lerps with disp3060 via slopeselector → dispA

dispA lerps with disp6090 via slopeselector → dispFINAL gets pluged into the displacement channel of my landscape material

this is using 5 lerps with the result of not getting tesselation on lod0
if i remove one of the lerps and compile i get tesselation on lod0!!!

it doesnt matter which lerp i remove the result is always the same…4 chained lerps GOOD…5 BAD!

im using the same setup for all the other material channels (normal, diffuse, roughness,…) with no issue (cant tell 100%, visually it appears ok) seems only the displacement channel is affected by this.
it would be awesome if a epic dev could chime in to tell me if this is a hard limit of if there is a workaround…else i have to reduce my complexity by one.