Are VOCALOID parts being played on multiple tracks?

Excess load is being placed on your computer's memory. Either freeze the "VOCALOID4 Inst", or turn off VOCALOID4 Insts on tracks that are not being used.

* It can be helpful to display "VOCALOID4 Synthesis Load" while you work, to view the load placed on your computer.
If the computer continues to be subject to excess load, the VOCALOID4 Inst will be automatically unmounted to maintain optimum performance.