ERROR Caught exception in ScannerThread.run() loop

[akhon]

rollbar-agent was working for years, and recently found a problem with it:

2019-10-10 21:36:52,985 ERROR Caught exception in ScannerThread.run() loop
Traceback (most recent call last):
  File "/usr/local/rollbar-agent", line 428, in run
    self.scan_all()
  File "/usr/local/rollbar-agent", line 444, in scan_all
    state = self.load_state()
  File "/usr/local/rollbar-agent", line 466, in load_state
    flag='n' if recreate else 'c')
  File "/usr/lib/python2.7/shelve.py", line 239, in open
    return DbfilenameShelf(filename, flag, protocol, writeback)
  File "/usr/lib/python2.7/shelve.py", line 223, in __init__
    Shelf.__init__(self, anydbm.open(filename, flag), protocol, writeback)
  File "/usr/lib/python2.7/anydbm.py", line 85, in open
    return mod.open(file, flag, mode)
  File "/usr/lib/python2.7/dbhash.py", line 18, in open
    return bsddb.hashopen(file, flag, mode)
  File "/usr/lib/python2.7/bsddb/__init__.py", line 364, in hashopen
    d.open(file, db.DB_HASH, flags, mode)
DBFileExistsError: (17, 'File exists -- BDB0002 __fop_file_setup:  Retry limit (100) exceeded')

and it doesn't delivers events anymore :(

rollbar-agent version 0.4.x
python: 2.7