I just loaded up a 1286 save into 1291 and I'm noticing a whole lot of merchant AI ships hanging out next to my colony just wandering about, doing nothing, not leaving. (Hopefully) save game attached.
#[fasttrack 1291] merchant AI ship swarm
near echo
Update - they're not doing nothing, they're apparently all correct, but I'm just seeing a heck of a lot more "transport incoming" messages than I used to.
That may be working as intended (it certainly is helping my colony!), but it does mean that there's a lot of merchant AI ships clogging the area around the planets. It's visually messy.