I’ve avoided using mirrors for a long time due to bugginess and complexities of the past, but had a really good use case so have been trying to use them again. Unfortunately I am still seeing some weird behavior. Here’s one issue…
In a list view grouped by heading and items sorted by priority, I changed the priority of a mirrored item (mirrored from one doc to another) from medium to high. It showed red but did not re-sort it, it stayed where it was. I quit and restart and it was still medium. I changed it again, it did not re-sort, I restarted, and then it was shown as red (good) but still sorted at the bottom below other medium and low priority items.
I’ve also seen a scheduled mirror item show up in Agenda view twice at different times, and then sometimes not show up at all at the time it is actually scheduled (and is visible at in the calendar day view).