Same issue, temporary solution found.
Stop platform on a curved rail, place inserter two tiles away from the track, so it loads items onto the hitbox of the turret, not the train.
Ver 0.4.6 used with SE, Krastorio and 30 other mods
Following attempts did not work on straight tracks with vanilla ammo/fuel:
-Loading platforms from both verticle and horizontal does not change the failure
-Loading platform from all 12 sides
-Used all vanilla inserters
-Used circuit logic to turn inserters off and on
-Loading platform after train has stopped at a station
Following attempts worked:
-Rotating orientation of inserter
-Replacing inserter
Inserter displays 'Waiting for space in destination" during all failure attempts