MSP430FR6047: USS echo signals in water pipe

Tool/software:

Hi,

I have a question related to USS signal echo captured by MSP430FR6047

If I extend sampling window, I notice the reported additional signal after the useful signal.

Sometimes the additional signal merges in the final part of useful signal, so it becomes difficult to distinguish them.

Do you have any idea of ​​the possible causes? Is this an echo phenomenon?

Could this be a problem for the acquisition accuracy?

How can the phenomenon be eliminated/reduced?

Thank you so much.