Cannot use effects on 3 or more instruments

I have a Scarlett 4i4 and I connected 2 guitars to the main analog inputs on the front (yellow circles on image1)

Then I connected a bass guitar to the input on the back (yellow circle on image2)

We can play all 3 instruments at the same time but only using the default amp without any effect.

If I set, for example, a distortion amp for both guitar tracks and select one of those tracks, both guitars work but the third instrument (the bass track) is muted

The only way to make the bass guitar work is selecting its track as shown in image3 (while taking the screenshot, instruments were not really connected, it's just an example image to show the overall scenario)

BUT at same time, the 2 guitars are switched back to "clean" sound, even though the distortion effect remains applied (in this example case named "flangilated lead")

Am I missing some GarageBand setting?Is this an hardware problem (related to USB audio Scarlett)?

Thanks for your help

image1

image2

image3

GarageBand version: 10.4.11