Error in HttpTask asynchronous

I’ve defined an HttpTask in my model and randomly it returns this fail:

2019-04-26 15:43:12.776 ERROR 2880 — [uire-async-jobs] o.f.j.s.i.a.AcquireAsyncJobsDueRunnable : exception during async job acquisition: null

java.lang.NullPointerException: null
at org.flowable.spring.job.service.SpringAsyncExecutor.executeAsyncJob(SpringAsyncExecutor.java:81) ~[flowable-job-spring-service-6.3.1.jar:6.3.1]
at org.flowable.job.service.impl.asyncexecutor.AcquireAsyncJobsDueRunnable.offerJobs(AcquireAsyncJobsDueRunnable.java:116) ~[flowable-job-service-6.3.1.jar:6.3.1]
at org.flowable.job.service.impl.asyncexecutor.AcquireAsyncJobsDueRunnable.acquireAndExecuteJobs(AcquireAsyncJobsDueRunnable.java:86) ~[flowable-job-service-6.3.1.jar:6.3.1]
at org.flowable.job.service.impl.asyncexecutor.AcquireAsyncJobsDueRunnable.run(AcquireAsyncJobsDueRunnable.java:62) ~[flowable-job-service-6.3.1.jar:6.3.1]
at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

Any sugestion?