If you're experiencing stutters after installing Sim Update 3 on MSFS2024, it might be due to simply opening the EFB to load a flight plan.
I found on my systen that flights using the default 787 were a stuttery mess after installing SU3.  These flightrs were smooth before SU3.  I then discovered that the stuttering started only after loading a flight plan using the Sim's built-in EFB.  In fact, I don't even have to actually load the plan to cause the stuttering. Just clicking the EFB's "Flight Planner" button is enough.
Here's a test you can perform:
1.  Start the Sim and select "Free Flight"
2.  Select the default "Boeing 787-10 Dreamliner" as the aircraft.
3.  Select a relatively "unconjested" airport and runway for the flight's departure. (I like to use KTRI - Runway 23)
4.  Start the flight and click the "Ready to Fly" button to place the aircraft on the runway, ready to takeoff.
5.  Switch to "External" view and pan around the aircraft noticing the "smoothness" of the panning.
6.  Open the EFB from the Top Menu, click the "Flight Planner" button and then exit the EFB.
7.  Pan around the aircraft as before and notice the "stutteriness" of the panning (or not if you're system is luckier than mine)
On my system this stuttering remains in effect throughout the rest of the flight session.  The only way to eliminate it is to exit and restart the Sim.  I have found this issue also applies (to a lesser extent) to the default 737MAX Passenger variant but not the Business Jet variant.  Nor does it happen with the default 747, Longitude, and any of the GA aircraft I tried.
If, when using the 787, I input the flight plan manually via the FMC and never open the EFB, my flights are as smooth as before installing SU3.
This post is mainly to provide information to others who may be experiencing this issue.

Confirm this issue introduced with SU3, observed on ini A330, ini A321, FBW A320 and A380 from what I tested so far. Tried also with C172 and had no problems. Indeed EFB flight planner is culprit,  I did a flight from KSTL to EDDF with default inibuild A330-300 without to touch EFB and had no weird stutters. I reported this bug on the microsoft official forum.

Edited August 24, 2025Aug 24 by David27

49 minutes ago, David27 said:

Confirm this issue introduced with SU3, observed on ini A330, ini A321, FBW A320 and A380 from what I tested so far. Tried also with C172 and had no problems. Indeed EFB flight planner is culprit,  I did a flight from KSTL to EDDF with default inibuild A330-300 without to touch EFB and had no weird stutters. I reported this bug on the microsoft official forum.

Interestingly, this issue was also noticed with the 777 PMDG in 2020 and 2024, with EFB on or off. And it was not reported or related to the flight planner, some claimed to be related to the Wt & Balance screen, or so. PMDG does it every few seconds; I checked the same with the IFly737, and no issues. 

Yup, major issues with the EFB on every plane. I’ve tested it myself, and if I don’t open the EFB during flights, I don’t get the mainthread stutters every 2 seconds.

I’m still in disbelief that they’d release the official build with all these issues. It’s like one step forward and ten steps back. It’s beyond me why they can’t just deliver a sim that works and stop adding features until it’s actually stable.