What is it?

You get these errors when running the Verify Data utility that indicates damage has been found in the company file. See Target Chaining
 

Why am I only seeing this now? I have been using QuickBooks for years?

Users may have upgraded to version 18.0. The errors were most likely always in the file and only the latest version of QuickBooks is making this issue prominent.

What caused it?

There are many factors that can lead to corruption in a QuickBooks company file. Here are the top ones:

• A large data file size and/or older file (usually starting around 1 GB or 10+ years old).
  

• Inventory in the file with items that were allowed to go negative.
  

• Server and workstations with not enough RAM.
  

• A slow network.

Is it fixable? Do I really have to create a new company file?

According to Intuit (the makers of QuickBooks), target chaining is not fixable, at least not by rebuilding the data file. However, if the transaction(s) that are causing the problem can be modified or deleted, then the problem can potentially be fixed. It just depends on how many corrupted transactions there are. I fixed a file where after just removing corrupted items from one of the transactions in the log file, it fixed the entire problem. 

But I still recommend that a new company file is created for the beginning of the next fiscal year. A fix may only be temporary until all list items that are corrupted are made inactive and not used again, especially in the case of negative inventory.