Institutional Shareholder Services, a prominent advisor to investors, has voiced concerns about Acciona. This concern is linked to an investigation involving one of Acciona's subsidiaries. The investigation is related to a specific case, though details about it are not fully provided here.

For more information on the case and its implications, readers can refer to the source. Further details about the situation and the investigation can be found in the original report, which provides more context and background information on the events surrounding Acciona and its subsidiary.