Actually, this is the first time happened. As long as I use Zendesk, never found FRT increased significantly especially in Zendesk Messaging, As informed by Zendesk Team that the FRT behavior is intermittent and unreliable on Messaging tickets in the Support dataset. Zendesk Team suggested to use Zendesk Messaging Dashboard to calculate FRT. I can't separate the 2 reports from the channels on Zendesk because they have an impact on the KPI team. Already reported to Zendesk on request (#10888510) but no result. This issue more than 1 month already.