Now is the time to take the gun apart and give it a very good cleaning.
The trigger group should be taken out and cleaned completely. Note: the 1400 and others of that series have many stamped parts inside, there may be dried grease/dirt causing the hammer to drop when the bolt slams into lockup.
Be careful with the plastic parts as replacements are very hard to find.
The 1200,1300, and 1400 models were Winchesters attempt to build a shotgun as cheaply as possible, the guns are good but I wouldn't be shooting 10 rounds of trap every week with one. Take care of it and it will last a long time.