Hello @dig,
Thanks for reaching out and welcome to our community 
I’ll be happy to help solving your issue, and to do so, could you please share some more details?
- What are you trying to do?
- In which context?
- What is your configuration?
…
The more info you’ll give me the easier I’ll be able to reproduce and tackle this problem.
Thanks!
Haven’t seen this error for a while
Hey there,
This issue popped up again and I worked out the cause. Thought it would be useful to flag as am sure many other clients encounter it.
If you create a segment, and the logic relies on a field which is hidden from view, then you’ll hit the error trying to save that segment. You can only set logic based on fields that are set to be visible in forest.
This is quite frustrating as we often want to filter based on fields that we hide from the table view in Forest.
Hello @dig
Thanks for working out the cause!
I’ll reproduce this on my end and create a bug report when i succeed to do so (or come back to you otherwise!)
We’ll update the thread once this is solved.
Yes I hid the file like that.
It is possible that the issue only occurs when the logic relies on a hidden field on a related data record instead of a field on the collection I’m creating the segment for. Let me know if that helps you reproduce.
Otherwise I can share private recording (as it contains sensitive data)
Little message to point out that we just had a quick session with @dig, and the issue is now fixed.
Thanks for opening a thread in our community, and also thanks for taking time to have a call with us today @dig 
Don’t hesitate to create any new threads on the community if you have any other questions 
Steve.