Complicated taxes - CPA making mistakes

[Bob Smith]

Curious what is acceptable.  Like many of you I have complicated taxes. I have 30+ properties, sales, purchases, multiple entities, different tax years, K-1's to send, k-1's received, W2 income, cap gains, cap losses, etc....

To keep things simple I will give an example of the type of thing that has happened on two recent tax returns:

1) It was an issue where an appraisal mattered.  Basis issue. I sent one appraisal and later got a better appraisal and sent that to CPA. They used worse one in rough draft.  At least $15k tax difference to me let's say.  Luckily I noticed.

2) Including property no longer owned in tax return. I assume they took the income from the year previous but we are not talking a trivial amount of money.  Let's call it $20k of income that I didn't really get. Luckily I noticed.

My CPA is not cheap so it's not like I am using someone based on cost. I am using a high level professional with a good reputation but I am concerned they are just too busy and the underlings don't get it done right.

For those that have complicated returns what is the accepted amount of material errors to see in a tax return?  Is one per year too many? I think so but want to make sure I am not being unreasonable.

What do you experts say?