Unfortunately there's nothing specific I can do to help you I fear.
It's probably an app or service that's being stuck causing this.
Don't use apps, mods or modules that aim to "improve" sleep behaviour by disabling integral parts.
Maybe a reboot helps, to determine if the problem is there from the start or surfaces after a while of uptime.
You can try to see with top command if an app/service is always on top consuming loads of CPU share, while the phone is idle. (Search the thread i explained here already how to use top command)
If you don't have at least an idea, try to pinpoint it by uninstalling apps in batches and use custom references in BBS.
Uninstall 5 apps, set custom reference in BBS, let phone sleep for 30 minutes without touching it and check BBS. Next 5 apps repeat the steps.
Could also be something in system is screwed up, try to set the phone up freshly without restoring a backup. Install apps in batches and check what's causing the problem with BBS.
It's not really the right place to discuss this here as it's not kernel related. So I suggest to create a new thread for troubleshooting if the issue can't be solved with above guidelines.