Unexpected end of JSON input causing ERR_INVALID_CHUNKED_ENCODING


I’m in the process of standing up Camunda 7.8 and I am running into an issue that happens on the tasklist. In the web browser console, there are two errors being throws show below in the image:

When these two errors are thrown the task process form updates with a message stating, “The task has been removed.” and a button to close the task appears, also the form title is updated with a strike through.

I have no idea what could be causing this to happen and any assistance would be awesome, thank you in advance.


Hi @freemanj,

could you please describe the steps until getting these errors?
Do you use an external task form?

If you have an JSON as process variable which is used in the task form, you could check whether the JSON is valid.



It happens in two instances, when walking the work flow of the form and when just sitting idle. The html for the form is in a .war file, I not quite sure if that counts as being an “external task form”. As for the JSON as a process variable I’m not quite sure, I will most definitely get back to you on that. Just a side not, this error was also thrown on the example bpm process that came with the download. I really appreciate your response!!


Hi @freemanj,

which example bpmn process did you start?

Do you have a stacktrace in the log file? Which runtime environment are you using?



Here is a screenshot of the error being thrown. Happens on the “Assign Reviewer” task from the Invoice process. The log file is also attach below. I’m using Java 8 runtime.

catalina.2018-01-05.log (68.8 KB)


Hi @freemanj,

there are some other exceptions in the log file. Could it be that the process instance doesn’t exist for the selected task? Could you please check in cockpit whether you have running process instances.

It looks like your bpmn process of your process application couldn’t be deployed because there is the following warning.

Warnings during parsing:

  • It is not recommended to use a cancelling boundary timer event with a time cycle. | priceChangeReviewProcess.bpmn | line 21 | column 61



Yes there instances running.

I do see the timer event defined in the .bpm file. Looks like there is a timer-transition to send an email. I’ll attach a copy of the .bpm file. If you could supply a recommendation for resolving this issue that would be awesome!

priceChangeReviewProcess.bpmn (5.3 KB)


Hi @freemanj,

thank you for sharing the bpmn process. It looks fine so far, but you could not have 2 sequence flows from the boundary timer event without a condition or a default sequence flow. The second hint regarding the process model, it is not allowed to have a timer definition of type cycle when you have a cancelling boundary timer event.

Back to the problem in the tasklist. Could you please share the price-change-review-form.html.



Good morning!!

Thank you for the suggested changes. I will make those as soon as possible. Below is a copy of the template. Thank you for your help!!!

price-change-review-form.html.txt (8.9 KB)

I changed the extension so that I could upload it.


Any progress on the issue?


Hi @freemanj,

sorry for the late response.

Before I will look deeper into the html form, we should make clear what are the steps to reproduce the error. For that, please undeploy your own web application and try to reproduce the error only with the example application. You wrote that you get the same error when you clicking on a task of this one.
When you can reproduce the error with the example application, it is easier for me to understand the problem.

Please do the following steps:
1.) Start the Camunda 7.8 platform with the deployed invoice example.
2.) Start a process instance of the invoice example.
3.) Go into the tasklist and click on a user task of the new created invoice process instance.
4.) Check whether you get the error again.



Ok cool, I’ll do that let you know the results. I’ll post screenshots or the errors once I replicate the issue. Thank you for your help!


Unfortunately I am not able to reproduce the error like before. If you take a look at the post where I sent you the log file, the error did occur. Figuring this issue is a high priority and will determine whether my company invest the enterprise version. If it’s something we’ve in our process that is causing this, steps to fix our process would be most helpful. To be clear, I very much appreciate your assistance :slight_smile:


Hi @freemanj,

I looked into the attached log file. But I can’t find an error related to the problem in the tasklist. There are the database exceptions which are not the reason for the tasklist error and which is gone after a restart of the tomcat.
You could try to reproduce your problem in the tasklist with your own process application. When you will get the error again, I need a stacktrace and steps to reproduce it.

Regarding my remarks to your process. I misinterpreted the sequence flows outgoing from the timer boundary event. It is correct to have one sequence flow from the timer boundary event to the send task and one from the send task to the user task. The one error was the timer event definition in the interrupting timer boundary event. When you change it to a non-interrupting timer boundary event, it is working fine.



So, I noticed in the pom file I neglected to change the parent dependency for Camunda from 7.3.0 to 7.8.0. This seems to have solved the issue, but it still occurs when the task list form is rendered and the browser becomes for 15 minutes or more. I am not sure if that is intend or if the cause still has something to do with the process we have defined. For this kinda solves the issue.


I’ll looking into more this morning, If I can cause it again I’ll send you the error snippets asap.