This is often caused by the box momentarily energising the hdmi output when waking from sby. On some TV’s (eg Panasonic TV’s using HDMI1 in), the port is auto selected by port activity (in a similar way to way HDMI auto switches select the last energised input). In this case using a different HDMI port may resolve. If however the issue is caused by a short loss of RF loop through during the boot, then a simple TV splitter to give the box a separate feed to both TV and box will sort it out. This will save you a bit of money in the long run as once the RF is split you can use low power sby on the box. I don’t have a 4000T so not sure which of the above is the likely culprit.