superunique not spawn in Act 5 map

[kaiya]

I added one new SU named Nihlathakbossnew，after editing theTXT files(Monstats/Superuniques/Monpreset/Obj) and also adding it to ds1，this SU can spawn in Act1~Act4 preset map，but in Act 5 preset map, the SU with Obj ID#51 and will spawn with a normal monster with HexID#291，txt file entries are:

Obj. txt
Act 5
Type 1
ID 51

Monpreset.
Act 5
ID 52 Nihlashakbossnew(by replacing original "place_nothing")

superuniques.
Nihlashakbossnew Nihlashakbossnew Nihlashakbossnew1 68 ……

Monstats.
Copy nihlashaknoss to the bottom and rename to Nihlashakbossnew1, HexId

Could someone advise how to fix this problem? Thanks.