VST instruments can consume a lot of CPU power. The more instruments you add, the more likely it is that you run out of processor power during playback.
If the Processing Overload indicator in the Audio Performance panel lights up or you get crackling sounds, you have the following options:
Activate Freeze Channel.
This renders the instrument into an audio file and unloads it.
Activate Suspend VST 3 plug-in processing when no audio signals are received for VST 3 instruments.
This ensures that your instruments do not consume CPU power on silent passages.