Legacy Objective Tree: Clicking on Key Results results in "Error Retrieving data for modal".

Issue Summary

This is reproducible on Data Center: yes

In the old experience of the Objectives tree, when we click on a Key Result, we get an error message: "Error retrieving data for modal. Please refresh and try again". 
Refreshing the page doesn't resolve the error

Steps to Reproduce

1. Go to Objectives Tree
2. Go to Program Objectives
3. In the column "Key Results," click on an Objective. 
4. The error message will appear.
5. If you try to refresh the page, the error will persist.

Expected Results

Open the Key Results.

Actual Results

The Error message will be shown—no error in the logs.

Workaround

Currently, we identified two workarounds for this behavior:

1. Access the OKR (Key Results) via Objectives, by clicking on the Objectives Hierarchy link, on the objectives page instead of by clicking the Key Results link;
2.  Use the new experience Objectives page, if it is enabled on the instance