Hello all. I would like to disclaim; I am limited in the information I can share due to its sensitivity.
Background:
The purpose of this flow is to take records from a daily generated excel report and see if those records exist in a Sharepoint list. If the record does not already exist, a new record is created. If the record does exist, the Sharepoint list record is updated using the info from the excel report.
Extracting and transforming the data from both sources, adding new records to the Sharepoint list, all no issue. The problem is updating records.
The process to match records between the two sources is as follows:
First, the records are loaded into individual select actions for final formatting. JSON Items comes from the excel sheet, Sharepoint items comes from the Sharepoint list.

Next, for each record in body(JSON_Items), this condition is evaluated:
If body(Sharepoint_Items) contains items('Apply_to_each')['ControlNo'] (the current ControlNo), update items, else create a new item. (the update action is not there yet, the array variables are there for further steps, please ignore)

Here is an example of a ControlNo/Account #:
000141597173-1234
To test the update feature, this is what I do:
I initiate a test run for the flow; today's report is added to the Sharepoint list. Once that test is complete, I initiate another test run for the flow, using the same report. In theory, these items should all show up as 'Update' items, since they all exist in the Sharepoint list thanks to the previous run. Unfortunately, in practice, this is not the result. Instead, it sees them all as new items, but when I view the outputs for 'Sharepoint Items' and CTRL+F the current ControlNo being evaluated from 'JSON Items', it always shows up.
So I know for a fact that the Sharepoint list DOES contain that ControlNo, but for some reason Power Automate is unable to find the match.
Any ideas where I am going wrong?
Hopefully I've clearly explained the issue, please let me know if I need to clarify or expand on anything.
Thank you all for your time and advice! - N. Bethea