EMC Troubleshooting speaker relay matrix

There is relay a matrix designed to switch between active and passive speakers in a music shop. There are actually two matrices, each in a different showroom. It has been observed that one matrix switches speakers almost inaudible while the other makes a quiet but annoying click. Here is a screenshot of a signal recorded at the output of the speaker relay matrix. This is matrix switching line signal for active speakers so it was possible to record it directly:

Recorded distortion on the output of the matrix, at the beginning and ant the end there are disturbances which I believe are 4 bytes digital transmissions coupled on the audio signal.

Because of the location and surrounding equipment only one rack with a matrix can be opened, namely the one which generates audible disturbances, it looks like this:

Wiring arrangement in the matrix

The matrix consists of daisy-chained modules, each module is switching one input signal to 1-of-8 output jack sockets. A single module can be simplified to the following:

Single module of the relay matrix

In reality a single module is more complicated (I assume GND is switched too) but it describes the idea. A complete matrix is built in two rows and wired like this:

Current wiring of 10 modules in the matrix (outputs not shown because they are shielded on the other side of the panel)

See how many times digital signal cable is crossing and running parallel to analog signal wiring. I believe there is magnetic coupling between digital and analog lines. To make it worse, both are wired without shield, such arrangement is actually prone to cross-talks and requires longer cables. I suggested changing arrangement to something like this:

Improved wiring of 10 modules in the matrix

In the improved wiring concept there are shorter cables, and there is no unnecessary zigzag. I believe this will remove unwanted disturbances on the switched analog signal. Rearranging is possible because every module has its own configurable address, I am not even sure what exact type of the digital transmission is used. Maybe daisy-chain order can be changed even without readdressing modules. I will update this post when it's done.

Fixing Ravensburger Tiptoi

Thanks to my college from work I had a chance to look at apparently popular toy called tiptoy. Basically it is a RFID infrared camera combined with a mp3 player. There are books with embedded RFID tags small points printed over the regular pictures. Those points are almost invisible to a human but tiptoy recognizes them and plays back some records when its tip touches tags in a book so a child gets interactive description of what is in the book. Different images or areas of images have different points pattern.
A typical problem of the tiptoy is that its speaker is not completely child proof and after some time the toy becomes mute. This particular toy worked with a headphones normal so my friend decided to try changing a speaker what solved his problem. Here come some pictures he took:

 Take batteries out, unscrew four screws.

 Take speaker out and desolder it.

Both speakers - the original one and the new not installed yet one.

This is close-up how the speaker is mounted.

You can ensure that the speaker caused a problem by measuring its resistance.

This is measured resistance of the new speaker, close to 8 Ohms is correct.

This is resistance of the damaged speaker. 2.3MOhms is almost open circuit - a speaker is damaged.