Hi there, we are suffering with issues of profiles not detaching correctly and users subsequently being able to log on. However our deployment is a WVD deployment with the VHDX files in azure files.
I guess you can either go on the host directly and attempt to detach the VHD in disk manager. or if you have access to the file server where the VHDX files are being held you could close the open file in computer management snapin under Computer Management\System Tools\ Open files
or if you are using Azure files you can close the handle in powershell online.
Get-AzStorageFileHandle
https://learn.microsoft.com/en-us/powershell/module/az.storage/get-azstoragefilehandle?view=azps-4.4.0
Close-AzStorageFileHandle
https://learn.microsoft.com/en-us/powershell/module/az.storage/close-azstoragefilehandle?view=azps-4.4.0