Stuck and stiff sora front derailleur
My SORA front derailleur cable broke (after gear change difficulties for several tens of kilometres, and ineffective cable length adjustments). I replaced the cable, but I still had to push the gear change lever very hard to change chain wheels (which is when I found this web page). The culprit was the plastic cable guide screwed onto the frame under the crank (GIANT Cross City 3). This guide had been cut through by the front derailleur cable and the cable had started cutting into the frame. After replacing this plastic guide ($3.00), as well as the cable, changing the chain wheel is almost as easy as when brand new.