Waves processors require large buffer sizes for smooth behavior in Digital Performer. This is even more pronounced at higher sample-rates.
Launch DP and go to Set up drop-down > Configure Audio System > Configure Studio Size.

Make a reasonable balance between the desired voices number and buffer size per voice.

A red warning will show on the bottom section of this window if your configuration is unbalanced.
DP also allows you to multiply the buffer size:
Under Setup drop-down, hit Configure Audio System > Configure Hardware Driver.

Enter a value in Buffer size. The value entered in the Host Buffer Multiplier multiplies the value chosen in the Buffer size field.
For example: If you chose 1024 in the Buffer size field and 2 in the Host Buffer Multiplier the total buffer size result will be 2048.
Note that large buffer sizes will ease CPU consumption, but also result in high latency.