PID are not handled correctly for fingers joints in ergoCubGazeboV1

[xEnVrE]

While using one of the robots that rely on GYP, namely ergoCubGazeboV1, I noticed that when setting the PIDs online, e.g., using the yarpmotorgui, the settings are not updated as expected.

The following video shows an example:

https://github.com/robotology/gazebo-yarp-plugins/assets/6014499/5ed9597c-38d7-473d-9724-8dd16fe2b9ab

I first command the index open/close joint r_index_oc, and it works as expected. Later on, I put the position P gain to 0.0 and I try to move the joint again. I expects it not to move, instead it does.

By testing the other joints, I realized that the r_index_add was not moving anymore. Hence, setting the P gain of r_index_oc has in fact changed the configuration of another joint.

Can be the fact that these are coupled joints the reason for this behavior - i.e., we are not handling PID setup correctly for these kind of joints?

cc @traversaro @Nicogene