400ex chain please help

Well ladys and gentleman i just recently bought an 01 400ex i dropped about 1500 into it so far and i am having a slight problem on my swingarm the back four allen head bolts that you loosin up to tighten your chain one of them got stripped well i tightened my chain and rode for about 5 min the chain poped off? well this continued till i finally put the bike up... Could that one stripped allen head bolt not bein tightened all the way down cause my chain to be comin off? Thank you very much