PowerQuery: Merge Expression Errror 'count' argument -- Help Please!!

I am trying to perform a merge query to see what UIDs are not in the first list that are in the second list and vice versa. I have two data sets with the following sizes:

List 1 = 1811 (CM)
List 2 = 1144 (HR)

When I try to do a merge JoinKind.RightAnti it works. When I try to do a JoinKind.LeftAnti it produces an error "Expression.Error: The 'count' argument is out of range. Details: -1"

JoinKind.RightAnti --> List 2 not in List 1 (success)
JoinKind.LeftAnti --> List 1 not in List 2 (failure) --> = Table.NestedJoin(CMMS_Combined,{"NUID"},#"HRIS Engineer List Simplified",{"NUID"},"HRIS Engineer List Simplified",JoinKind.LeftAnti)

What I have tried:
1. I have verified that all duplicates for the UID linkage key in each list are removed.
2. I have verified all nulls from UID field are removed.
3. I have trimmed all UID fields.
4. I have capitalized all UID fields.
5. I have converted all UID fields to text.