Diagnosing a loose Bottom Bracket is a routine maintenance job. Which is a good thing because this is a regular occurrence with ALL types of BB systems.
How to spot a loose BB
Firmly hold the bike steady and attempt to move the crank from side to side – in the opposite plane of motion to its rotation. If there is any play from side to side, the BB system is loose.
An open/loose BB will need its bearings adjusting (via the adjusting cup) or replacing. If you diagnose a loose BB in any other type of unit, such as BB30/90s and outboard bearing units, the first thing to check is the attachment system of the cranks and/or BB spindle.
Click here for more information on fixing BB issues.