The static Titan Launcher (and this is especially important with the AT variant) is too low to aim/fire over a sandbag wall that is on even ground in front of it.
This also applies when placed in a small bunker (Objects/Fortifications). The raised variants of HMG and GMG are high enough, as the soldier is standing.

The soldier should probably kneel a bit higher or something, the use of a static launcher out of a fortificated position is of severe tactical importance for a defense situation, at least in my opinion.