Errors with scheduling API workflow on lists


I need help understanding a weird issue with backend workflows.

I have two similar backend workflows that each run on two similar lists. The workflows are meant to take the items in each list and create a “task” in Bubble.

If I schedule the workflow to run on a single list, it works perfectly and will create a new task for each item in the list. But if I include the second list and run the second workflow on that list, the workflow will leave out items from the second list, and naturally does not create tasks for those missing items.

Basically, I can run a backend workflow on a single list and it works, but if I include more than one lists, or run a similar backend workflow on one or more lists at the same time, items go missing.

What am I doing wrong and how can I get the workflows to run through the entire list regardless of how many there are?

Thank you

How many items are in tour list? And are these two scheduled in the same event?
Could you share a screenshot of the WF.

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Thanks for replying. The number of items in each list varies, but its no more than 4 items each.

I may have gotten it to work today, so I’ll spare you the details. But if I continue to have issues I will update the thread.


I guess it’s deciding not to work again, so any assistance would be helpful. I will provide a clearer breakdown of my issue as well as provide a video at the end if that will make it easier.

I have a data type called “Video Ads”, a data type called “Tasks”, and a few option sets.

For context, these option sets are a list of aspect ratios for either Facebook, Instagram, Snapchat, TikTok, or YouTube. The number of aspect ratios in each list varies but there are no more than 4 options each. In Total, 13 items.

For further context, during the creation of a new Video Ad the user can select from a list of social media channels they want their ad to appear on and doing so will allow them to select the aspect ratios for the respective channel, adding the selection to the Video Ad’s list of aspect ratios.

All of the above works fine. I explained it to give context to the setup. But here is where I encounter an issue. At this point, I want to take the selected aspect ratios for each channel and create a new “Task” which is to be added to the Video Ad. To do this, I’ve created a different but similar backend API workflow to run on each list of the Video Ad’s aspect ratios.

The backend workflow does the following.

  1. Creates a task
  2. Adds the task to the video ad’s list of tasks.

The issue is that the tasks are created in Bubble, but if more than one of these backend workflows run, it will not fully complete the step where it ads the task to the Video Ad’s list of tasks.

If I run it on 1 list, it works, but once I go over 1, some items are added, others are not. If I select all 13 aspect ratios, sometimes only 7 will be added, if I do it again, sometimes only 2.

Here is a video that demonstrates what I just described.

Could you share a screenshot of how you call the backend WFs as well.
This looks like an issue with how bubble runs each WF parallelly. One workaround on the frontend would be to set each API call in a custom event.

Have you gone through this post here?:

I got a extremelly similar problem.
I have two list of dates and I pass them through scheduling API workflow on lists one after another. It is the same backend workflow and very similar to yours, having the following steps:

  1. Create object “work day”, that has a date (the date of the list) and a number (1 for the first list and 0.5 for the second, this number is passed as a constant argument when schedulling the WF)
  2. Make changes to an Object (same object for both lists, passed as a constant argument when schedulling the WF). It adds the created “work day” to a list in the object.

The global idea is that I have two list of days, one for full day work and one for half day work, and I want to add the dates as “work day” objects in a list.

It sucessfully creates all “work day” objects (steps 1) but sometimes it does not save them in the list (step 2), even though the “make change to thing” action is called in the log, even with the right id of the list were the “work day” is supposed to be saved.
And also, I’m using “result of step X” to refer to the “work day” when saving it to the list, so it should be safe, accordinly to the other reply.

Weirdly, after searching for a solution, I’ve executed again (with no changes, but different date lists) and it worked all the times now, but I do not trust it.
I’ll try again later

Backend WF:

Schedulling WF:

And after trying some more times, it happend again. It created 8 “work day” (4 from the first schedulling and 4 from the second) objects but only added 1 to de list.


API schedulling :

Creating objects and supposedly adding them to the list (not all entries, but you get the ideia):

Only the “work day” 06/04/2022 was actually added to the list

Hello guys,

Someone among you has found the solution? @vicente1 , @randreas ?

I clearly have the same problem and I don’t see an answer on the forum.

Any help would be appreciated :sweat_smile:

Hello Dimo

Unfortunately, I no longer have access to the client’s app for which I had this problem. I was able to solve the issue, but I cannot remember how. I’ll try to dig into my notes and see what I can find.

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Hi randreas,

Thank you for your quick response !

Ha heck … it’s sad if you found the solution haha.

Thank you for taking the time to search :grin:

Same issue here - workflow on a list works for some of the items but not consistently and not all items. If it threw an error in logs or something (and if I knew what error to look for) that would be one thing, but this seems to be silent fail. Anyone got any clues?

Do not use “Schedule workflow on a list” it silently skips things, even with lists of 4 things I’ve had it forget one of them :slightly_frowning_face:

Never had problems with “Schedule workflow on a list”, except the limit of 255 items in a list.
In the case on the video above it’s clearly a race condition that Randreas organized occasionally. Two or more workflows are trying to modify the same thing at the same time, so the last modified item overwrites one that’s been modifier just a moment earlier. You need to show your setup to understand what’s going on in your particular case, but this one is definitely not about “Scheduling workflow on a list”.