di2 front derailleur jumps when shifting down
 

Hi, I just got a new bike with Shimano di2 R8050. All is working good, except when I shift my front derailleur down it does a slight jump (chain slips) after about a second or a bit less. If I have it on the bike stand (no load), I can not notice anything. It needs to be under some load. Not changing gears under high load, just normal riding. Any idea what this could be? Taking it back to the bike shop they might keep it for quite a while, and not too sure about their mechanics start with. Might be something simple I hope. Front derailleur works perfectly apart from this.

== Update ==
On the bike stand I can replicate this condition by applying slight brake to bake wheel - shift down under slight load(normal riding). Can see the chain does not fit into lower chainwheel. Could something be assembled incorrectly? I have photo, but can not post is here(Get error message " You are not allowed to post URLs until you have at least 10 posts".). Photo taken as chain just starts shifting down. Half the chain is still on the large chainwheel at time of photo. Any way I can post photo or URL to photo??

It is supposed to do that.
Overshifts a bit for a quicker shift and then realigns.

Hi Dean, thanks for quick reply. Maybe my description was not too good. The chain actually slips after a second or less after shifting the front down. It is definitely not supposed to do that. None of my previous bikes, or other di2 bike does that.

Adjust the limit screw so the derailleur doesn't move as far.

This is your answer. The derailleur needs adjustment. If you're a decent mechanic, download the Dealer Manual for the groupset and follow the (very easy) instructions. If you take it to the bike shop for adjustment, it should take less than five minutes once they start work on it.

The low limit stop on the 8050 Di2 is electronic. The upper stop is an adjustment screw.

Put the bike in the small chainring and the largest cog.

To adjust the low limit press and hold the junction box button till you get the red light (half second or so). Then push the left shift lever button until there is a clearance of .5 mm between the inner FD plate and the chain.

Press the button on the junction twice when you're there, and you're done when the lights go off. I just installed mine last week. Adjusting is simple.

http://si.shimano.com/pdfs/dm/DM-R8050-01-ENG.pdf

this is the correct answer.

Thanks for taking the time to explain it here. I did this during a ride for a friend that was getting a bit of chain rub while cross-chained(52-28).

Silly me, my Di2 was in Semi-Synchro mode. So, when I shifted the front to small chainring, the rear shifted about 1 second later. I thought this was a jump or slide in front, but in actual fact it was the rear shifting after the front finished. I put it back into manual mode by pressing button twice until green/red LED flashes once only. All good! Thanks for all the other helpful replies too!