PowerBI Ambiguous Relationship Path Error

Hi DarylK_MA ,
The error appears only when you switch T6 ↔ T7 to 1:1 with Both-direction filtering because that change makes every leg in the ring fully symmetric. At *:1 the engine still gives one side (the 1 side) a higher internal priority so it quietly picks a single path. At 1:1 that priority disappears, so two active, equally valid routes exist between T4 and T7 and the model surfaces the ambiguity.

Core idea: a closed loop + multiple Both-direction relationships + peer (1:1) links = ambiguity.

Practical fixes (pick one):

1. Keep it Many to one and change some links to Single direction to break the loop.
2. Before switching to 1:1 set at least one other relationship in the ring to Single so only one full path remains.
3. Make one relationship inactive and use it only when needed:

Alt Path Measure =
CALCULATE ( [Base Measure], USERELATIONSHIP ( T6[One], T7[One] ) )

1. Merge T6 and T7 if they are always 1:1 and queried together.
2. Redesign toward a star schema (avoid circular bi-directional chains).

Optional sanity check for hidden duplicates:

T6 Duplicates = COUNTROWS(T6) - DISTINCTCOUNT(T6[One])

(Repeat for T7; expect 0.)

Key guidance: minimize bi-directional links, prefer a star layout, use inactive relationships or TREATAS when you only need an alternate path occasionally.

References:

• Create and manage relationships in Power BI Desktop
• USERELATIONSHIP function

Let me know which option you lean toward and I can outline the concrete steps.

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