Originally Posted by
dreamingant
Additionally, a friend took it out to test it and he seems to think that it felt like there was something possibly wrong with the cable - said it felt too squishy when he shifted. So, yet another theory.
Cables don't "squish"- your friend doesn't know what he's talking about.
I've heard from others that excess lube can cause the chain to not catch on the chainring pins, which creates problematic shifting after lubing. Wipe off any excess, and then thoroughly wipe off the chain and chainrings again. However, that's also an indication that the derailleur's outer limit screw isn't set properly.
I agree with FB: if the mechanic you took it to can't fix it,
get a different mechanic. Making a front derailleur work correctly is something any bike mechanic should be able to handle.