[SalesForce] Process builder flow fails because it hasn’t been set or assigned – Tried other fixes

I am running into the same error as i have seen on other forums but all the fixes are not solving my issue.

The process starts when a contract is created or edited.

Then i check to see if a field on the contact of the contract has a particular value. The formula is:

[pba__Offer__c].pba__Contact__c.Retail_Lead__c="Yes"

However on running the process i get the following common error.

The flow failed to access the value for myVariable_current.pba__Contact__c.Retail_Lead__c because it hasn't been set or assigned.

A common fix was to handle that either the contact may be null or the field i am accessing may be null, so i have included the checks to see if both a null as follows:

AND(NOT(ISNULL([pba__Offer__c].pba__Contact__c)),
NOT(ISNULL([pba__Offer__c].pba__Contact__c.Retail_Lead__c)),
[pba__Offer__c].pba__Contact__c.Retail_Lead__c="Yes")

This still did not fix it.

I also tried to use a condition before my main check to validate if any of the fields were null, however the error was still there.

The only thing i can think might be the issue is that the "Retail Lead" field is a formula, should that cause any problem?

I have tried to use but it has the same effect:

|FLOW_ELEMENT_ERROR|The flow failed to access the value for myVariable_current.pba__Contact__r.Retail_Lead__c because it hasn't been set or assigned.|

I am hoping it should look something like this

Please note i am using PropertyBase which is basically sales force with custom objects.