Let's see... let's start by taking inventory. THREE lost fumbles for turnovers in that game.
Fumblers, who all fumbled?
Here are the ones I recall, supplemented by SI box score.
https://www.si.com/nfl/game/2142043/box-score
* Penny, 1 carry, 1 fumble LOST (seemed that way, maybe a couple other carries too)
* DK, 1 beastmode-type catch and run play, with one unfortunate fumble, LOST at the end
* Russell, 1 fumble LOST (or was it two) while being sacked, and I think there was one other one possibly.
* Ifedi, 1 misguided run attempt, 1 fumble LOST
* Carson, 1 fumble (recovered)
I think Russell's fumble gets counted as "recovered" and Ifedi's fumble clearly gets counted as LOST.
2 of the 3 LOST fumbles were the result of punch-outs by the SF defense. I don't know about Penny's fumble. Anyone have a good look at how that happened? Was it on Penny, or was a SF defender in the backfield on the handoff?
Cure... we hope...
* DK, Rookie, now he's got experience and knows what it feels like to have the ball stripped at key plays in a game. Twice this has happened. Experience? Coaching? Practice? I think this one will improve right away. Mainly better judgment about when to extend, and when to keep the ball secure. This was a strip that resulted from him giving extra effort, trying too hard. That said, it's BS that an out of bounds defender can strip the ball and have it ruled a fumble. NFL needs to revisit this rule. If OOB player touches ball and forces fumble, any lost ball should come back to the point where the player first touched the ball while OOB. On punts, this type of play gets flagged as unsportsmanlike conduct. Not a 100% direct parallel, but the idea is that the game is played IN BOUNDS.
* Penny, don't know. Didn't really see the cause of the fumble. Since we hardly saw him after that, it must be on him in Pete's mind.
* Carson, more focus on ball security. He improved, then regressed. In fairness, he gets a lot of carries, in tough situations. Just needs to get that focus back.
* Russell, that fumble was just the game and stuff that happens sometimes when you have 3 big mean guys trying to rough you up. You know he'll review and analyze and try to fix anything that can be fixed.
* Ifedi, Coaching and practice, hang on, get down!!
The most fixable are Ifedi's, and DK's fumbles, and maybe Carson's. Ifedi won't get many more opportunities ever to fumble, and would probably get excited and have a brain meltdown anyway, regardless of coaching. DK you know will fix it. Carson, fix it again. Russell, keep balling out, shit happens, keep being yourself and making plays. Compare Wilson's ball security to Garoppolo's, and Russell looks like a bank vault.