Use a tool to push sideways on the joints and from the component side.

Bad looking joints can still have a connection even if they look bad. If the connection has truly come loose, there will be some movement in the joint.

When we were working on surface mount boards, we would use a sewing needle and run it down the pins, and listen to the sound. The needle crossing a solid pin will make a sharp sound. If solder joint is not good, the pin moves, and you will get a duller sound. Dink, dink, dink, dut.