internal pressurization test

I am doing a simulation of a Prestressed concrete containment vessel for
internal pressurization test. currently i have made a 3D concrete model
and embedded a reinforcing structure and tendons into it using embedded
region option. but during analysis, it is showing that ratio of
deformation speed to wave propagation speed exceeded 1 in some elements
and the job is getting aborted. someone pls help me figure out what
could be the reason. I have attached my input file for
reference......thank you....