QB Issue Resolution:

This is a known issue with pro, intuit says they are working on it, well they said that several months ago

All you can do is wait for a fix, while waiting …

In Desktop, back up the file then use the main menu File>Utilities>Rebuild and Verify run it as many times as necessary (but at least 3 times) until it completes, then close QB and re-open it and see if it helped

And try entering the bill, then paying the bill for inventory items

Resolution for Issue 'Assembly items error stopping me from entering a check' available: Yes (Solved).
Source: Intuit Community forum.

Assembly items error stopping me from entering a check: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for assembly items
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Error Recovery for assembly items [Canada]
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