workflow error -50001

Hi guys,

I'm currently struggling with an error that's happening at a certain step of my workflow.

When I try to approve my document to a certain stage, I get this error:

But the Attribute is created and configured correctly.

I noticed that this attribute is currently being used as a trigger to a select statement for another attribute:

I tried to make that Attribute editable and manually change its value, and also got this error:

But if I remove this attribute (REV_TYPE) from the trigger of the REV_NEW attribute, I can edit it and the workflow works.

Also, if I add another attribute as a trigger for the REV_NEW attribute, this new attribute also display an error when updating.

This is the place in the rules engine where the attribute is being updated:

Can anyone help me with that?

I tried all I could think of, and nothing seems to work.

Thank you!