If you are experiencing crackling audio while using automation FL Studio, it is likely due to the plugin or parameter you are adjusting.  For example, some plugins require lots of processing power when adjusting parameters, which could cause crackling when combined with the rest of your project playing. In these cases, you can try creating automation of a less CPU-intensive plugin that still produces a similar result to what you want. Click here for more tips on how to Fix Crackling In FL Studio