Traps are pretty much bomb proof to be honest !!! However clays ain't and if the get juggled around slightly in transport or even banging slightly when trap filling hair line cracks can appear and cause hassle !!! Generally speaking we work on 2 percent no birds but things can go wrong such as a broken clay can bend a seperator knife slightly , bend an arm slightly and in the heat of a comp can easily be missed .battery power is crucial especially with remote controls used rather than cables , I now throw all my batteries out when they are 18 mths old and start again , yes you still get the odd one that creeps through the charging cycle without being full .
remember machinery never breaks down until it is being used , and any mechanical thing will break eventually so it's how you approach the problem when it's occurred is the key , I personally tend to keep a spare trap handy as this is normally the quickest way to resolve the problem and carry on .