Are you all carefully monitoring your accounts after flights & hotel stays? I find it astonishing how often you get an incorrect amount of points or no points at all.
I haven't kept any statistics, just off the top of my head I would say that around 50% of the time I have to file a claim.
That's why I sometimes think that those hotels and airlines should give bonus points each time they give you a run for your points or miles.

This month so far:
Hilton & Marriott posted correctly
Accor: got points for the stay, no points for the extras (food). Was solved in a matter of days
Iberia: points for 3 flights out of 4
AA (credited my wife's Iberia flights to AA as that is her main account) : 1 flight out of 4 posted incorrectly. Showed up as Economy while we flew Biz

I’ve not run into this with UA and other airlines I’ve traveled recently but have run into this a few times with Marriott stays over over the last couple of years. As a result I do monitor my accounts fairly regularly after a trip to confirm appropriate credit while details are still fresh. I also get itemized final bill (by email or hard copy) before leaving premises just in case..

50% would be an astronomical number. I would estimate closer to 1% for me.

My only issue is that I often have no clue how many miles I should earn for certain flights (e.g. if distance based you need to know the fare code plus multiplier and if fare based you often need to know the portion of the fare that is applicable along with your personal multiplayer on the day of travel).

You just need to be a little more OCD and then you will know this for every flight without having to look up the multipliers in a chart.

Do you credit your miles to the airline that you've flown or do you also sometimes credit to partner airlines.
If I solely look at those flights that I credit to the airline that operated the flight the statistics look slightly better, most problems seem to occur when you credit to partners.
I recently flew LATAM and credited to BA: outbound flight OK, return flight is missing.

1% is really good, surprised it works so well for you.

Yes, it does require some bookkeeping but for most airlines you're able to find all the information you need. Flyertalk is a really good source of information. I learned a lot on this forum.

I can't remember the last time I've ever had anything post incorrectly or not post. I know it's happened to me but it's been years. Even 1% is probably an overstatement.