What do you mean with #3? A command like below runs perfectly fine with no PS* specific junk.

``` > Get-Process | Select -Last 5 Name,ProcessName,Company,Path | ConvertTo-Json [ { "Name": "winlogon", "ProcessName": "winlogon", "Company": null, "Path": null }, { "Name": "WmiPrvSE", "ProcessName": "WmiPrvSE", "Company": null, "Path": null }, { "Name": "WMIRegistrationService", "ProcessName": "WMIRegistrationService", "Company": null, "Path": null }, { "Name": "Zoom", "ProcessName": "Zoom", "Company": "Zoom Video Communications, Inc.", "Path": "C:\\Users\\user\\AppData\\Roaming\\Zoom\\bin\\Zoom.exe" }, { "Name": "Zoom", "ProcessName": "Zoom", "Company": "Zoom Video Communications, Inc.", "Path": "C:\\Users\\user\\AppData\\Roaming\\Zoom\\bin\\Zoom.exe" } ] ```

And when you say "Just the common '|fl XXX' expression will trigger this" does that mean you are doing this `<command> | fl X | ConvertTo-Json`? Because if so, that's why your getting all the PS specific junk.