This is a known problem with some VSTis and plug-ins. It’s especially problematic with ramp tempo changes - you can usually get rid of the problem by approximating them with a bunch of step changes.
As mentioned above, the plug-in / VSTi needs to adjust to the new tempo every time it gets a new tempo - that takes time and can cause audio dropouts if the tempo changes occur too quickly. A ramp change is passing tempo changes as quickly as it can because it’s trying to create a continuous change, so the audio processing has much less time to catch up between new tempos. Step changes are discrete, so many fewer tempo changes passed to the plug-in / VSTi and it has a much easier time keeping up.
You can still get problems with step changes but they’re much less likely than with ramp changes.
In my orchestral template, I have to set Kontakt to “internal” tempo reference for this reason. If set to “external” (i.e. sync to host) then I get crackles during ramp tempo changes.