I have a question about firing torpedoesT1(G7a) manually,everytime my torp. exploded halfway

,the first time I fired two torp.with a distance of 1600m and the second time from 600m.
It's my first campagne mission.
Mod's are:
OpsMonsun_V705
OMv705_to_V720
OMv720_Patch5
OMEGU_v300
OMEGU_v300_Patch7
OM_Med_Env
OM_Pac_Env
Henny