QB Issue Resolution:

it sounds like you have recall previous transactions set to on in company settings

what is happening is when you create a new bill, QBO is filling in the old bill entries trying to make life easier for you, what you should do is delete the line QBO enters for you and enter what you need, or turn off the setting

Resolution for Issue 'how do i enter a new bill for an existing supplier with outstanding bills already entered.' available: Yes (Solved).
Source: Intuit Community forum.

how do i enter a new bill for an existing supplier with outstanding bills already entered.: 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 existing supplier
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Error Recovery for existing supplier [Canada]
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