If tapping helps/hurts, it's a sure sign that some solder needs to be re-flowed... Here's something I've been working on:

https://drive.google.com/file/d/0B_Xp3uN-BcxsRThRU1NOQ1RXR1k/view?usp=sharing

Look at L2, L3, C15 and P1

Also: look into replacing C15 if it's original