Google translation from French:

Hello,

I intend to acquire vegas 18, I downloaded a demo but unfortunately the sound cracks when I use external plugins (waves for example)

I cannot work with this software

A solution ?

Vegas Pro does not support VST3 so many 3rd party audio plugins to not function properly or at all in Vegas Pro. Waves has been raised as problematic in Vegas Pro a number of times on the forum, and a comment in the following post notes that Waves has not been compatible with Vegas Pro since Waves version 9.6:

https://www.vegascreativesoftware.info/us/forum/waves-plugin-causes-lag-crash-in-vegas-when-plugin-window-is-open--126321/#ca786373

From Waves' compatibility webpage:

https://www.waves.com/support/tech-specs/supported-hosts#version-9-6

Vegas Pro is a supported host for version 9.6 but does not appear in the later versions.

Please note that Vegas Pro 19 is the current version of Vegas Pro, and replaced 18 about 2 months ago. It would therefore not be expected that there will be any more development of Vegas Pro 18. You might be better off testing the trial version of Vegas Pro as this is the version for which future development will occur, though at the moment Vegas Pro does not support VST3 plugins either.