It looks like you caught a bug. It is a beta feature (and Projects is new), so there are probably more bugs than usual. You can report it by clicking Gear>Feedback, where there is a Bug choice
Resolution for 'Bug choice issue: 'Customer Types on Past Transactions' available: Yes.
The Bug choice 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 Bug choice issue yourself by looking for a resolution described in the article. If it is a complex Bug choice issue or you are unable to solve the issue, you may contact us by clicking here or by using other Bug choice support options.
For more information about resolving issues related to Bug choice in Quickbooks/QBO or to get support for the issue 'Customer Types on Past Transactions', click the link below: