Ram Gopisetti
Ansys Employee
which part of your question do you think there is a bug.
"My surprise comes after checking the results, the residual velocity from matsum increases with time, ~73% higher in contrast to the expectedreduction," what quantities are you referring here (x_rb velocities or anything) try looking into history of the eroded elements as follows

or this
"I am also puzzled by the eroded kinetic energy, since it reads zero"------------"No Bug on this issue"
Are you seeing any failure in elements, you have to see it ? post down your queries below.
version used was 11.0 MPP
Cheers, Ram