Had a thread here a while back when I was having a real problem with Apex shifter / FD combo on my wife's bike.
Turned out it was MY problem - anchored the cable wrong. But int he process of figuring it out I did swap the FD for a Shimano FD (ultegra).
So the bike shifts pretty well now both front and back. Only issue is if you're going uphill and don't get into the small ring early enough and shift with some pressure at low cadence. Sometimes it just won't go into the small ring on the first shift, and it takes a second or third shift. If you're familiar with Apex shifters you know the loud click-click when shifting into the small ring. Well, you hear that noise, but the derailer doesn't move. So you just hit the shifter again, and usually the second try does it but occasionally it takes three or four attempts. Each time you get the click-click but no derailer movement.
Is there something wrong with the shifter? Is something just not engaging? Or is there an adjustment I'm not aware of that I can make on this thing?
Does it happen when you're not going into a climb? As in just pedaling on a flat course?
I'm assuming you're on the big ring and shifting into the small ring coming into the climb.
The "mid" click between the big/small shift in the shifter is trim function. This places the FD cage in-between the big and small rings to avoid chain rub at extreme gear combinations (big-big, small-small).
Shifting the FD under heavy load (i.e. climbing) is generally considered a no-no. The chain is under a lot of tension and will the FD cage will generally have a hard time pushing the chain onto the small ring. So even if you shift (disengage/release the ratchets on the shifter), the FD may not move as it is pushing against a tensioned chain. If it does shift, it may cause the chain to jump and cause chain suck - even with the low limit screws properly set. Worse, it may even break the chain.
Downshifting on the front before big efforts is generally the correct way to go.
If the problem persists I think that you have the shift cable adjusted too tightly.
Happens more on a climb than flat but occasionally on flat. It's my wife's bike, and part of it is her not shifting soon enough, but I've ridden it and it happens to me - even when I lighten up on the pedals while shifting. Riding the same hills I ride my bike on (with 105 triple) and shifting the same way I always do on my bike...have not problems with my 105, but this Apex shifter /ultegra FD combo just won't get it right. THe weird part is that all you have to do is shift it a second or third time and it works - -the first time it's just not moving the derailer.
Now I did read (via google search) that possibly could be related to bad B tension setting. I might try that.
Yep, I know. Just going by something I read specifically about Apex group where someone with a very similar problem to mine corrected the B tension and it affected the way the front shifting worked to move from big to small ring. I don't really get it either, but it's worth a few seconds to check on the B tension to be sure it's good.