Trailer uses the model of TrailerM967tankerBase (with details in TrailerM967tanker.txt), but is missing details that make tires not appear and storage containers inaccessible.
Rewrote TrailerM967_WaterTrailer_RS.txt file (see below).

Just copy and replace.




module Base
{
/**************Code changes by Tread ----- (Trealak on Steam) *****************/
/**************Textures and original vehicle script by KI5 *****************/
/***** Original Truck, most of its parts, parameters, model, overlays etc. by KI5 *****/
/***** Tire and storage fixes by biotwister *****/


model TrailerM967tankerBase
{
mesh = vehicles/Trailers_M967tanker_Body|M967_trailer,
shader = vehicle_norandom_multiuv_noreflect,
invertX = FALSE,
scale = 0.1,
}
vehicle TrailerM967Water
{
mechanicType = 2,
offRoadEfficiency = 2,
engineRepairLevel = 4,
playerDamageProtection = 1,

model
{
file = TrailerM967tankerBase,
scale = 0.9000,
offset = 0.0000 1.1444 0.3222,
}

skin
{
texture = Vehicles/Trailers_M967watertanker_Shell_USMCgreen,
}

skin
{
texture = Vehicles/Trailers_M967watertanker_Shell_desertTan,
}

skin
{
texture = Vehicles/Trailers_M967watertanker_Shell_NATOgreen,
}

skin
{
texture = Vehicles/Trailers_M967watertanker_Shell_civilian,
}

textureRust = Vehicles/Trailers_M967tanker_Rust,
textureMask = Vehicles/Trailers_M967tanker_Mask,
textureLights = Vehicles/Trailers_M967tanker_Lights,
textureDamage1Overlay = Vehicles/Trailers_M967tanker_Overlays_Damaged01,
textureDamage1Shell = Vehicles/Trailers_M967tanker_Damaged01,
textureDamage2Overlay = Vehicles/Trailers_M967tanker_Overlays_Damaged02,
textureDamage2Shell = Vehicles/Trailers_M967tanker_Damaged02,
extents = 2.5111 1.4889 6.3333,
shadowExtents = 2.5555 8.6221,
shadowOffset = 0.0000 -2.5557,
mass = 875,
physicsChassisShape = 2.5111 1.4889 6.3333,
centerOfMassOffset = 0.0000 0.5333 -2.4222,
engineForce = 5000,
engineQuality = 60,
engineLoudness = 55,
maxSpeed = 60f,
brakingForce = 1,
stoppingMovementForce = 2.0f,
rollInfluence = 0.15f,
steeringIncrement = 0.03,
steeringClamp = 0.3,
suspensionStiffness = 40,
suspensionCompression = 4.83,
suspensionDamping = 3.88,
maxSuspensionTravelCm = 15,
suspensionRestLength = 0.16f,
wheelFriction = 2.5f,
frontEndHealth = 150,
rearEndHealth = 150,
seats = 2,

wheel FrontLeft
{
front = true,
offset = 0.9222 -0.8000 -3.6889,
radius = 0.60f,
width = 0.60f,
}

wheel FrontRight
{
front = true,
offset = -0.9222 -0.8000 -3.6889,
radius = 0.60f,
width = 0.60f,
}

wheel RearLeft
{
front = false,
offset = 0.9222 -0.8000 -5.0333,
radius = 0.60f,
width = 0.60f,
}

wheel RearRight
{
front = false,
offset = -0.9222 -0.8000 -5.0333,
radius = 0.60f,
width = 0.60f,
}

area TruckBed
{
xywh = -2.0000 0.2778 1.4889 1.4889,
}

area TruckBed2
{
xywh = 2.0000 -0.6333 1.4889 1.4889,
}

area TruckBed3
{
xywh = 2.0000 -2.1778 1.4889 1.4889,
}

area TireFrontLeft
{
xywh = 1.8222 -4.0889 0.4444 0.4889,
}

area TireFrontRight
{
xywh = -1.8222 -4.0889 0.4444 0.4889,
}

area TireRearLeft
{
xywh = 1.8222 -5.4667 0.4444 0.4889,
}

area TireRearRight
{
xywh = -1.8222 -5.4667 0.4444 0.4889,
}

template = TiresV100A3,

part TireFrontLeft
{
model InflatedTirePlusWheel
{
file = TrailerM12Xwheel,
}
}

part TireFrontRight
{
model InflatedTirePlusWheel
{
file = TrailerM12Xwheel,
}
}

part TireRearLeft
{
model InflatedTirePlusWheel
{
file = TrailerM12Xwheel,
}
}

part TireRearRight
{
model InflatedTirePlusWheel
{
file = TrailerM12Xwheel,
}
}

template = Suspension/part/SuspensionFrontLeft,
template = Suspension/part/SuspensionFrontRight,
template = Suspension/part/SuspensionRearLeft,
template = Suspension/part/SuspensionRearRight,
template = Trunk/part/TruckBed,
template = M967Storage,
template = M967TrunkDoors,

part TruckBed
{
container
{
conditionAffectsCapacity = false,
capacity = 100,
}
}

area FuelStorage
{
xywh = 2.0000 -0.7222 1.4889 1.4889,
}

template = RS_WaterFilter,
template = 10000WaterTruckTank,

container
{
conditionAffectsCapacity = false,
}

physics box
{
offset = 0.0000 2.0000 -0.4556,
extents = 2.2333 1.2889 9.0333,
rotate = 0.0000 0.0000 0.0000,
}

physics box
{
offset = 0.0000 2.2222 4.3556,
extents = 0.1111 0.1111 0.5889,
rotate = 0.0000 0.0000 0.0000,
}

attachment trailer
{
offset = 0.0000 0.0556 2.9111,
rotate = 0.0000 0.0000 0.0000,
canAttach = trailerfront,
}
}
}