NullReferenceException when processing job

We are using Hangfire to schedule service calling. It was working fine all the way…

As queried from Hangfire db, the status stuck at processing and never succeed or failed, and i found that it hit null reference exception when try to perform the job:

2020-03-25 19:00:08.0146|Debug|AppStart|Hangfire.Server.Worker|Worker.Execute => Worker.TryChangeState => NLogLogger.LogException
State change attempt 1 of 10 failed due to an error, see inner exception for details
System.NullReferenceException: Object reference not set to an instance of an object.
at Hangfire.Common.JobFilterProviderCollection.d__4.MoveNext()
at System.Linq.Buffer1..ctor(IEnumerable1 source)
at System.Linq.Enumerable.d__a01.MoveNext() at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()
at System.Collections.Generic.List1..ctor(IEnumerable1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at Hangfire.Common.JobFilterInfo..ctor(IEnumerable1 filters)
at Hangfire.States.StateMachine.ApplyState(ApplyStateContext initialContext)
at Hangfire.States.BackgroundJobStateChanger.ChangeState(StateChangeContext context)
at Hangfire.Server.Worker.TryChangeState(BackgroundProcessContext context, IStorageConnection connection, IFetchedJob fetchedJob, IState state, String[] expectedStates, CancellationToken cancellationToken)

Any idea what is the reason caused this? It was recovered after a recycle app pool.