Tuner rack input faulty

[Dusk]

Hello talkbass tech dudes who know all things and can fix stuff!

here it is:

I have a combo amp that has the Fender RT1000 tuner rack in it

The tuner works fine with the front input of the tuner

The Tuner out from the back of the amp works fine (tested) - this would go to tuner input at the back of the tuner rack

Tuner rack works if i connect Tuner output on back of amp to the input on the front of the tuner rack

So in short,
I rate the tuner input at the back of the rack is faulty... as nothing happens there...

i would like to be able to use my mute to tune ability with the tuner rack without having cables flying everywhere (ie from tuner output behind the amp all the way around to the front of the tuner rack input...)

Has anybody had a problem like this before?
what could the problem be?
Is it DIY-able?

any input is appreciated

Many thanks