There is no ultimate loader:
3.215 Script @DoubleSpeedBelts/data-final-fixes.lua:26: local prototypes =
{
{type = 'transport-belt', name = 'transport-belt', tier = 1},
{type = 'transport-belt', name = 'fast-transport-belt', tier = 2},
{type = 'transport-belt', name = 'express-transport-belt', tier = 3},
{type = 'transport-belt', name = 'basic-transport-belt', tier = 0.5},
{type = 'transport-belt', name = 'turbo-transport-belt', tier = 4},
{type = 'transport-belt', name = 'ultimate-transport-belt', tier = 5},
{type = 'underground-belt', name = 'underground-belt', tier = 1},
{type = 'underground-belt', name = 'fast-underground-belt', tier = 2},
{type = 'underground-belt', name = 'express-underground-belt', tier = 3},
{type = 'underground-belt', name = 'basic-underground-belt', tier = 0.5},
{type = 'underground-belt', name = 'turbo-underground-belt', tier = 4},
{type = 'underground-belt', name = 'ultimate-underground-belt', tier = 5},
{type = 'splitter', name = 'splitter', tier = 1},
{type = 'splitter', name = 'fast-splitter', tier = 2},
{type = 'splitter', name = 'express-splitter', tier = 3},
{type = 'splitter', name = 'basic-splitter', tier = 0.5},
{type = 'splitter', name = 'turbo-splitter', tier = 4},
{type = 'splitter', name = 'ultimate-splitter', tier = 5},
{type = 'loader', name = 'loader', tier = 1},
{type = 'loader', name = 'fast-loader', tier = 2},
{type = 'loader', name = 'express-loader', tier = 3},
{type = 'loader', name = 'purple-loader', tier = 4},
{type = 'loader', name = 'green-loader', tier = 5},
{type = 'loader-1x1', name = 'loader-1x1', tier = 1},
}