Why is data in cell disappearing?

[MCB123x]

Hello,

I'm using this formula: =$C$8:INDEX($C$8:$C$28,MATCH(REPT("z",255),$C$8:$C$28)) which creates a list to use in another column which has an array formula: {=IFERROR(INDEX(JN,MATCH(0,COUNTIF(JN,"<"&JN)-SUM(COUNTIF(JN,C$7:C7)),0)),"")} which puts the list in ABC order and combine duplicates. All is well until I entered a duplicate name and that said name disappeared from the list. It reappeared after I enter another duplicate name but another name disappeared. I have no idea why this is happening. Any and all help is appreciated.

Thankyou

 

[Peter_SSs]

Duplicate to Disappearing Data when duplicating text

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