@Queenbernoski1 Another suggestion: if you have Sims 4 on another platform or system, the Grim Reaper's Rewards carry over from PS to XBOX, etc. on the same screenname. So, if you have a second copy of the game (and the Base Game is free now) you can play that one and you will have the rewards on both (unlike the paid DLC). (This was my plan if I couldn't get my game to work after it crashed.) Also, send your Sims and houses to The Gallery, which is cross-platform, if you are able to use it. You can download your creations again if you ever have to start over with the free Base Game version, etc. The Rewards (and the Reaper's Event activities) are cross-platform on the same screenname (as long as you claimed them).
If you are on XBOX One and already planning to upgrade to Series S or X, the faster processing speed is sometimes able to read cloud saves with some corrupted files from XBOX One, and you can go in and delete the corrupted files from Library if any (a red X will be visible if corrupted). On PS, you can't clear the cache but you can use USBs, so I like working that way. If you already have a PS4/5, you can download Sims 4 for free, you won't have any paid DLC, but if you use same screenname, you can continue with the Reaper's Rewards Event. Also, if you have any older save games from September or before the Reaper's Event, try loading one up, see what happens, maybe the mailbox trick will work on an older save (try Old Rusty and/or Willow Creek).
Worst case scenario: salvage what you can of your creations and and send them to Gallery. That way, you can use them again if you have to start over (though that doesn't solve Rewards issue, it allows you to continue with your own Sims and houses).
Also, get as many of the other Grim's Rewards points as you can because there are more Newsletters after the first week. Not sure if that will work, but get as far as you can with it because there will be more Newsletters and maybe the game will be prompted to send the old one or give you options. Also, if you don't have the Paranormal DLC, it gives you added opportunities to get points, not sure if that would help, but I thought about this when I was stuck waiting for the Newsletter (on a copy without it). Finally, turn off all Lot Challenges (besides Scare Seeker when they prompt you to add it), the Mold Lot Challenge probably crashed my game. This may be fixed now due to the most recent patch, but I am not sure, and I am leaving Lot Challenges off (except Scare Seeker). Build Mode has been glitching lately so I am using it sparingly until this Event is over. Also, I am avoiding: travel to other lots, festivals, following teens to high school, university life, etc. For Rent, Cupid's Corner, or unnecessary tasks until I finish this Event. As far as CAS Mode, try using it from the mirror, sometimes it resets a few things when you get back to Live Mode (like the mail carrier or position of mail carrier).
I really hope one of these suggestions helps! Also, I hope Newsletter and mailbox issues are patched out.