If the transducer receptacle is "loose" it is broken.
The unit is still on the flat rate repair charge list, but you may not want to spend that much on that unit. The price includes whatever it takes to get you a functioning unit--even replacement. The list is on the Humminbird website.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1