Microsoft Graph - Training Campaign - POST request has stopped working

I write an automation which uses Microsoft Graph API and endpoint /security/attackSimulation/trainingCampaigns . All any POST requests worked couple days ago (until mid/end August 2024). Today I noticed that POST request fails with an error code 400. Could you please check whether "trainingAssignmentMappings" body section has been recently changed?

I tested "code examples" from an official documentation and they does not work any more https://video2.skills-academy.com/en-us/graph/api/attacksimulationroot-post-trainingcampaigns?view=graph-rest-beta&tabs=http

I tried send a POST request from Microsoft Graph website, PowerShell script using Invoke-WebRequest and with cmdlet New-MgBetaSecurityAttackSimulationTrainingCampaign from Microsoft.Graph.Beta.Security. In every case it returns status 400 (BadRequest)