I bought a Trek FX Series 7.5 in April 2017 and ride every day for about an hour. Two weeks ago the crank arms suddenly gave around the bottom bracket and no longer stayed 180 degrees to eachother. I "fixed" this at first by simply tightening the screws on the crankarms. Last week the problem recurred and I took it to a bike store. 

The repairman showed there was actually a spacer in the bottom bracket which broke off, which caused the BB and crankarms to wiggle side to side slightly. He put on a new spacer, gave me the bike, but today the problem recurred. 

I don't have any experience repairing more serious problems like this, so I have a few questions. Given my explanation and the photos provided, can anyone guess as to what the cause of crankarms not staying 180 to eachother is? Is it indeed a broken BB? 

If so, is this the type of thing that is fixed or should the component be replaced? Should more components than just the BB be replaced?

Any help is greatly appreciated. Thanks. 

[![enter image description here](https://i.stack.imgur.com/BQdwm.jpg)](https://i.stack.imgur.com/BQdwm.jpg)

[![enter image description here](https://i.stack.imgur.com/yhx7k.jpg)](https://i.stack.imgur.com/yhx7k.jpg)

Edit: The picture below shows the problem in greater detail. The "spacer" I was referring to isn't part of the bottom bracket, but the crank arm. Also the chain ring bolt had broken/fallen off. The technician put a new chainring bolt and just screwed the crankarms on tightly. As a solution I have bought new crank arms, same model, both right and left. Thanks for the help!

[![enter image description here](https://i.stack.imgur.com/Aej0q.jpg)](https://i.stack.imgur.com/Aej0q.jpg)