The marked solder joints tend to crack when exposed to repeated heating and cooling.

Make sure that there is a connection between C points in the second picture - if there's a resistance or open line add wire bridge as described with green line from C to C point. This is power so DO NOT use signal wires/kynar.

Note: While you have your soldering iron out make sure to inspect pretty much every other solder joint on the board and re-flow it if necessary.