Help please - Parking sensors

Hi all,

After laughing at the stealers for £82 per sensor i bought from German ebay. All was fine got the sensors today and they work lovely.
But my other (original 2) now don't seem to sense at all.

I have put the new ones at each end of the bumper, so original in the middle 2 holes - does this make any ods???

Also just realised the sensors are different numbers;
original = 4b0 919 275f, new ones = 7h0 919 275f

Apparently these are the same part, can anyone confirm??

Any light shed is very welcome...

Ah that is interesting then - thanks.

I am pressuming they should work in harmony!

Going to try moving there places tomorrow and see where that gets me...