Where do you live (nearby postcode) and which transmitter do you receive from? Is the problem on all channels? If not, which are the problematic channels? Do you normally feed the TV aerial via the 5000t?
The signal could be too ‘fine’ with your new aerial. What are the signal strength/quality readings from the 5000t and the TV (when you can get a picture even if it’s blocking)?
There are high pressure atmospheric ‘lifts’ on at this time that can cause co channel interference causing picture breakup.