1. Verify that the joint shaft is not twisted or cracked.
2. Turn the joint shaft by hand and verify that the bearing rotates smoothly and freely.

Drive shaft
Joint shaft removal/installationMazda 6 Service Manual: Contact Authorized Mazda Dealer and Have Vehicle Inspected
If any of the following warning lights or the indicator light turns on/flashes,
the system may have a malfunction. Contact an Authorized Mazda Dealer to have your
vehicle inspected.
...
Mazda 6 Service Manual: Automatic Brake Operation Display (Type A Instrument Cluster)
“Smart City Brake Support activated” is indicated in the active driving display,
and “Smart City Brake Support Activated” is indicated in the multi-information display
after the SCBS brakes or the brake assist (SCBS brake assist) is operated.
NOTE
The collision warning beep sounds ...