Truncation of vector type means you’re plugging a larger vector type into a small input slot, e.g you’re using a Vector4 (r, g, b, a) from a texture sample and you use that as input for an operation that will only use (r, g, b) components and output a Vector3. The original fourth component, a, will not be used and will be lost after the operation. If you want to get rid of the warning you can use a ComponentMask to filter out components of a vector.
When you get data from a texture like this you’re defining a “sampler”. Each sampler has settings for things like filtering and how they should handle UV coordinates that are outside the original texture. In ps_5_0 (Pixel Shader for Shader Model 5.0) you can only have 16 of these samplers per material. Basically you’ve got too many textures in your material.