The definition of AssaultModule in StarbaseModuleDefs.xml looks like that:

  <StarbaseModule>
    <InternalName>AssaultModule</InternalName>
    <DisplayName>AssaultModule_Name</DisplayName>
    <Description>AssaultModule_Dec</Description>
    <ShortDescription>AssaultModule_ShortDec</ShortDescription>
    <Icon>GC3_Assault_Fighters_Icon.png</Icon>
    <SpecializationType>Generic</SpecializationType>
 
    <!-- Stats -->
 
    <Stats>
      <EffectType>ModuleConstructionPoints</EffectType>
      <Scope>Queue</Scope>
      <Target>
        <TargetType>StarbaseModule</TargetType>
      </Target>
      <BonusType>Flat</BonusType>
      <Value>1</Value>
    </Stats>
 
    <Stats>
      <EffectType>InterceptorFightersCap</EffectType>
      <Target>
        <TargetType>Starbase</TargetType>
      </Target>
      <BonusType>Flat</BonusType>
      <Value>5</Value>
    </Stats>
 
    <Stats>
      <EffectType>Maintenance</EffectType>
      <Target>
        <TargetType>Starbase</TargetType>
      </Target>
      <BonusType>Flat</BonusType>
      <Value>0.4</Value>
    </Stats>
 
    <Prerequ>
      <Techs>
        <Option>HighCapacityCarriers</Option>
      </Techs>
      <UpgradesFrom>InterceptorModule</UpgradesFrom>
    </Prerequ>
 
  </StarbaseModule>

As you can see it sets InterceptorFightersCap, but shouldn't that be AssaultFightersCap? At the moment if you have both AssaultModule and InterceptorModule installed on a starbase I suspect you will only get 5 interceptors, but no assault fighters ... ?