Hello,
I will try to keep this as concise as possible as I have been wracking my brain the entire day trying to figure this out.
Problem
I have 3 environments, Dev, QA and Prod. I have a solution which contains a collection of entities, a couple of flows and some option sets. I have exported and imported this solution from Dev to QA and Prod a couple of times with no issues. However, today I decided to change a field in Entity A to look up on from Entity B in the same solution instead of the System Users Entity. After doing this, I tested to make sure I could create/edit records in Dev and it worked. Exported/imported into QA and everything worked. Importing into Prod is where the trouble happened. I received this error intermittently:

A flow I had connected to this entity also had an error stating this:

The flow error remained constant however the Query Builder error seemed to be intermittent for multiple users. It was really odd that I could create an entry sometimes and other times I could not. Eventually, the error became more and more common until it was consistent.
What I've tried
- I ensured I removed any remnant of the old field that a replaced with the new lookup field. If it matters, I did name it the same. Note - I have another look up field that I essentially remade during troubleshooting and I named that something different but it is having a similar issue.
- Used a few XRMtoolbox plugins to see if I could find any reference of the attribute. Nothing showed up having to do with the old fields.
- I tried updating data using the "edit data in excel" function but that yielded the same result as the flow.
- I tried removing the Lookup fields from the forms and import/exporting into prod. I noticed that after doing this, one of the option set fields would throw the error shown above so if I left it blank, I could create items. This was intermittent as well.
- After seeing this, I tried removing the problematic option set from the solution and reimported. It seemed like this was the most consistent way to create records with no errors.
- I tried creating the relationships manually instead of letting CDS do it when you create a field.
- I've deleted all data in prod just in case previous data from the old fields messed things up.
The most bizarre thing to me is everything works perfectly UNTIL I use my prod environment. I also can't understand how it would create records sometimes then the very next record, using the same data, throw an error. I am out of ideas as to how that environment has issues when everything I use is within the same solution.
Apologies for the wall of text here. My head is swimming and I felt like all of that detail may help someone smarter than myself help me. Please let me know if I can provide any further details that may assist.