The Bunny PC just installed this 400MB update. No improvement at all.
Faulting application name: ForzaHorizon4.exe, version: 0.0.0.0, time stamp: 0x5bb7917b
Faulting module name: ForzaHorizon4.exe, version: 0.0.0.0, time stamp: 0x5bb7917b
Exception code: 0xc0000005
Fault offset: 0x0000000000d77191
Faulting process ID: 0x805c
Faulting application start time: 0x01d461d4fcc4df57
Faulting application path: C:\Program Files\WindowsApps\Microsoft.SunriseBaseGame_1.197.899.2_x64__8wekyb3d8bbwe\ForzaHorizon4.exe
Faulting module path: C:\Program Files\WindowsApps\Microsoft.SunriseBaseGame_1.197.899.2_x64__8wekyb3d8bbwe\ForzaHorizon4.exe
Report ID: 93c7d396-b849-456c-9c55-3ce8bab4d94b
Faulting package full name: Microsoft.SunriseBaseGame_1.197.899.2_x64__8wekyb3d8bbwe
Faulting package-relative application ID: SunriseReleaseFinal
It also generated a crashreport.xml (but I have no option to attach that file.)
The previous version suicided just as dramatically:
Faulting application name: ForzaHorizon4.exe, version: 0.0.0.0, time stamp: 0x5bb6b107
Faulting module name: ForzaHorizon4.exe, version: 0.0.0.0, time stamp: 0x5bb6b107
Exception code: 0xc0000005
Fault offset: 0x0000000000d77161
Faulting process ID: 0x188c
Faulting application start time: 0x01d461d45fe81fb6
Faulting application path: C:\Program Files\WindowsApps\Microsoft.SunriseBaseGame_1.197.396.2_x64__8wekyb3d8bbwe\ForzaHorizon4.exe
Faulting module path: C:\Program Files\WindowsApps\Microsoft.SunriseBaseGame_1.197.396.2_x64__8wekyb3d8bbwe\ForzaHorizon4.exe
Report ID: 2154b170-f050-4e4f-a976-8e5a5a246252
Faulting package full name: Microsoft.SunriseBaseGame_1.197.396.2_x64__8wekyb3d8bbwe
Faulting package-relative application ID: SunriseReleaseFinal
close all applications overlay as msi afterburner running with osd.
Confirmed! Rivatuner statistics server was the fault behind mine!!! Thank you sooooo much!
After 1.197.899.2 my game work´s until i press any button at the pre-rendered season change menu… it laggs/stutters 2-3 times and crashes in a grey window.
Not even a error message… just back at my desktop and thats it… i tried this “guide” https://www.thewindowsclub.com/forza-horizon-not-working-properly
But no dice 
Nothing unnecessary running in the background : Msi Afterburner and alike. Except Soundblaster soundcard driver and Logitech Gaming Software
Nvidia driver 416.34
win10 1809 17763.55
R7 1700 @ 4ghz
Gtx 1080 @ 2ghz
corsair 16gb 3200mhz
Running into this issue as well. Game worked just fine until the last update. Now it just crashes when I click “Continue” on the main menu. I’m reinstalling the game now to see if that helps. I have also installed the latest Nvidia drivers.
I have same issue, game ver 1.197.899.2, so after last update starts crash on menu when click Continue.
This is not relevant to GPU drivers, Windows updates etc. Last update of Forza made my game completly unplayable
The solution for me was to reinstal the game and then all the dlc´s
But i had the teredo-thing blocking every mutiplayer content…
Then i looked in the xbox app : Options/Network and there it shows if teredo is certified… if not there should be a link for troubleshooting : Xbox Support
the link looks something like that… i apologies the link is in german so even if you dont understand anything it says… basicly it says right click the explorer to open PowerShellAdmin and spam all the following prompts 
netsh interface Teredo set state disable
netsh interface Teredo set state type=default
reg query HKLM\System\CurrentControlSet\Services\iphlpsvc\Teredo
netsh interface Teredo set state type=default
reg query HKLM\System\CurrentControlSet\Services\TcpIp6\Parameters
reg add HKLM\System\CurrentControlSet\Services\Tcpip6\Parameters /v DisabledComponents /t REG_DWORD /d 0x0
and restart… then i looked at the xbox app again and no problem what so ever… everything was activated and NAT was open