There's an old critical bug in Logic Pro X that cannot be corrected by Apple for about 5 years. There are many forum topics dedicated to this, people even refuse to use the program because of this.

The first bug is incorrect plugin delay compensation (PDC) while sidechaining from aux track with latency-introducing plugin, the second is incorrect automation latency compensation (ADC) using a latency-introducing plugin.

Video with PDC bug demonstration

Video with ADC bug demonstration

This bug is ruining the workflow completely on big projects or for UAD users or for precise automation tasks or for external devices, etc. The program is unusable because of this.

People are trying to report it continuously using Logic Pro Feedback page but still no luck.

The most complete discussion

Another big discussion

We want Apple to prioritize fixing this bug.