"There not much I can do about this it's out of my control
"
I disagree ! Suspect you are using FFTC and the last link is via overhead wires (= aerial) ?
You could block that frequency for the parallel mode = interference and pass it for differential = signal.
The Mk2 filtered faceplate is said to do this - (no one is providing details and I suspect it doesn't work well all the way down to 26 kHz - possibly that end isn't too serious as signal is stronger and radiation of REIN is less efficient - ) 26 kHZ is a wavelength of 11.5 km so doubt if the overhead line is an appreciable fraction of this so a poor aerial.
It depends on how important it is to you and if you are prepared to spend about £10 for an uncertain result.
Unless someone has performance figures for the Mk2 ?