Don't know exactly what you are referring to in the picture. All I can see is a closeup picture of the chainring area of your bike. 21 speed bikes use a narrower cassette than 24 speed bikes, so chain angles at the extremes are worse on your current bike than they were on your older ones. even then, using those extreme angle gear combinations isn't good for your drivetrain. You need to have your derailleur adjustments checked by a good bike mechanic. It is your bike shop's responsibility to repair the problem you are having, they are supposed to repair or replace the defective part which they will send back to the distributor for warranty replacement. Cycles Lambert can be difficult to deal with for a retailer, but you have to be persistent with them to have the problem repaired