In reply to muku_383:
Use instead of a queue a uvm_tlm_analysis_fifo. This is the dedicated storage element for your scenario.
wrt to your problem:
env_ptr.f_scb[obj.f_dest_addr].tx_q.push_back(obj);
In the build_phase you are using the agent number as argument. In the write function you are using the dest_addr of your seq_item. This might not be the agent number. And the index might not be contigious.