Utterly perplexed why I'm getting error messages when refreshing this model

Hi masplin 
Please check the below points.
IncomeGroup[Min]/[Max] call the measures [Total Population] and [Av annual Net Income], which scan all of MSOA_Mapping including [Income Group]/[Income Tgt], which are built from Min/Max. That loop is what breaks the rebuild.

Three quick edits fix it:

1. Add a plain column: MSOA Population = CALCULATE ( SUM ( 'Age by MSOA'[Population] ), 'Age by MSOA'[Year] = 2024 )

2. In Min and Max, replace the AVIncome VAR (drop the measures):
VAR AVIncome =
DIVIDE (
SUMX ( MSOA_Mapping, MSOA_Mapping[MSOA Population] * MSOA_Mapping[Net annual income after housing costs (£)] ),
SUMX ( MSOA_Mapping, MSOA_Mapping[MSOA Population] ),
BLANK ()
)
Keep the rest of Min/Max unchanged same result.

3. Set MSOA_Mapping[LA Name] → Property[LA_name] to single-direction (keep it Active).

Note: never call a measure inside a calculated column on a table that measure scans.

Make those three changes and refresh sorted.

Thank you.