Nothing impressive this time.
The game worked fined but with a crackling sound.
As usual I checked all the traces but didn't find any broken.
So it was time to pull the V ROMs (4 of them) and compare them with the MAME romset.
V1 to V3 were fine however V4 wasn't.
This ROM has a Toshiba reference but is pin to pin compatible with a standard 27C800.
So it was just a matter of programming the .v4 file in it.
After resoldering the 4 V ROMs, sound was restored and 100% perfect.