I think I may have noticed these type of latencies...but not 100% sure.
I also have removed/reduced the delay when ramping volume on a Denon AVR using RS232.

I also had a macro that turned on some shared sources. I used a sense trigger event to start the macro. The trigger comes from 12V trigger on a B&K CT600. So, when any zone turned on, the shared sources turned on.

Problem was: Due to the XP8's ability to multitask... the triggered event was happening in the middle of my other macros (during programmed delays)... and making the programmed macros take longer.

I changed the order of things a bit, and "fixed" the issue. In fact, this is a FEATURE... but I just wasn't used to it, and took a few attempts to get good results. Overall, I love the sense event triggers and the ability to multitask.