@Rustler:  Are you familiar with QB Enterprise?  I seem to remember that it can combine reports from different company files.  If so, maybe they could switch to cloud hosting of Enterprise (albeit at a much steeper cost)?

Resolution for 'consolidation issue: 'consolidation of three companies' available: Yes.

The consolidation 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 consolidation issue yourself by looking for a resolution described in the article. If it is a complex consolidation issue or you are unable to solve the issue, you may contact us by clicking here or by using other consolidation support options.

For more information about resolving issues related to consolidation in Quickbooks/QBO or to get support for the issue 'consolidation of three companies', click the link below: