Most of those commitments are in writing, by contract or email, so I first send them a copy and ask, "where are we on this ?"   I give them the benefit of the doubt that it is an oversight, there is a delay or they are still working on it.   If they just aren't going to honor their commitment, then I have to work to get it resolved otherwise and get the deal done for my client.   After all, THE CLIENT COMES FIRST !   After that, then it's time to reevaluate whether this person is truly a member of "the team" and treat them accordingly in the future.

Depends on the issue and how it's resolved.  I use vendor I have trust and if the trust is gone so is the vendor.

Tony and Suzanne Marriott, Associate Brokers - if it is in writing, simply show them.

If it is not in writing and important - get it in writing.

Now if they fail, we have something to show them...

No more 'He said, she said'.....

I deal with it the best I can.  I also make note of them and never will use their services again.

Tony and Suzanne Marriott, Associate Brokers Hold their feet to the fire.

Lenders and Inspectors rely on agents for the purchase business and they should realize that if they fail to do something, they are not going to get any future business from you.. Buyers and Sellers are different, since agents need them to earn a paycheck. I hate to use THE word, Depends, but it does. Figure out the problem, and understand this is your business and expect nothing but the best. Anything less, and they are gone.

I sometimes have a discussion and other times I just drop them

if I can't rely on the word of a "team member" then they're off the team....it's an easy fix.... it's business.... no room for emotion.... 

I tend to spell things out which takes time. When ignored, my phase two is an accountability dart that hits the target thrown at. Business is not a game

Depends on what it is. But I certainly follow-up and remind them, especially if there is an email where they said....

I go to their office, jump on their desk and do the gorilla. 3:)
Seriously, this rarely happens, fortunately. If it does, we take immediate action to find out what happened and get it fixed. If not past the point of no return, will replace the offending party. If offending party is a client, will liberate them from the relationship.

It varies on what the circumstance is.  I work with the best and it's rare I run into problems.

Inspectors, Lenders, and other professionals are dealt with by promoting the service they provide.

Buyers and Sellers are presented questions that reveal the cause. Based on the revealing, I assess what the future holds.

Sometimes folks need a reminder, others need to be replaced.