Hope you don’t think I was being flippant. You obviously wouldn’t change it for changes sake.
When you say the picture is jumping, you mean the whole picture or does the picture break up with small boxes appearing (pixellation)with sound issues too?
Does this happen if you connect the aerial directly into the TV (bypassing the YouView box)?
It is very coincidental to happen when you have replaced the aerial. Perhaps the new one has a lower gain. If the connections remain unchanged (assuming you simply unplugged to old and plugged in the new), then you could try a signal booster.
I am not familiar with YouView boxes. Does it have an option within a menu to tell you signal strength and quality? If so you could check there and report back. I know the Humax HDR FoxT2 has.