Link to instance
As we can see below, function setLockDuration() only checks for MaxLockDuration and not minLockDuration. This is problematic since users can set _duration to be lower than the minimum. This has no problem outside the lockdrop event since the minimum lock duration is only specific to lockdrop events. In the lockdrop though, the calls would revert for users having lock times less than the minimum due to this check here. This is not a big issue since users can just extend their lock durations to the minLockDuration. Enforcing the minimum check would be helpful though.
Solution: Check if the _duration parameter passed by user is greater than equal to minLockDuration, only if lockdrop event has started i.e. block.timestamp is greater than start and less than end time of the lockdrop event. This would ensure users are not forced to extend their lock times to minLockDuration when there is no lockdrop occurring and users are locking tokens just for schnibbles earning. 
