Hi,
This could be due to the large set downloaded to the device from a single transaction in the database. Do you have some kind of BG processing which update data as bulk? In this case data records were downloaded to the device and device is still processing them and storing them in the local database. So until device completes that task, it will not delete this transaction ended message. In this case your are downloading Grouped Push related data. Worth checking the Sync Data volume screen in IEE to see you have large data set for GP related entities.
How long does device stay in this state? If you go to the sync monitor of the device, can you see any status messages? Also please take a look at the device logs (Physical device) to see any errors.