>>1479417have you checked the height ?
when they are new some FD have a sticker to help line up the height
bear in mind that the FD moves upwards as it moves away from the seat tube of the bike
if its too high the chain will be thrown off the largest chain ring, and there will be some effect on downshifts
if corrections to height or angle are ineffective
it may pay to quickly check how worn the chain is
bicycle chain pitch is 12.7 mm between the center of each chain pins
the inner plates put pressure on the rollers that wear into the chain pins
also check your cables and shifter body's for build up of grime or rust
clean and lubricate any junctions and pivot points
derailleurs themselves often need less cleaning than the parts that actuate them
