DB Adapter stopped polling the record from the database table however the process health looks good

If the BPEL process health looks good, there is a chance that you could find error message in the log files about primary key value null.

If the DB Adapter is polling using the logical primary key (ie. database table doesn't have primary key on the table)  and the primary key value is null in at least one field of a record then that record will be picked and after that stops proceeding further.  This record will be in stuck positon.  And all the subsequent records won’t be polled.    So, delete all the bad primary key based records.  Then the remaining process will continue picking up by the Db adapter as usual.