On a 16:9 TV I find that via scart I need to change the aspect on the TV not the SD Humax. The 9300T user guide states that the wide button is for when you are connected to a 4:3 TV. For a 16:9 TV the 9300T user guide states that you need to adjust the TV – not the Humax.
Are you using SCART or HDMI?
Have you switched from using SCART to using HDMI?
Have you switched from using HDMI to using SCART?
Presumably you are using a 16:9 TV?
Is the Humax aspect ratio still set to 16:9? MENU >> Preferences >> A/V control.
It may be also due to brodcasting error. Have you any recordings which you have already played OK but no longer play OK?