Go to the folder of sounds
'Steam\steamapps\common\railworks\Assets\RSC\ES44NSHP\Audio\RailVehicles\Diesel\ES44\Cab'
and copy the file 'T_ES44_E-BELL.dav'. Then go to the folder
'Steam\steamapps\common\railworks\Assets\RSC\ES44NSHP\Audio\RailVehicles\Diesel\ES44' and paste there.
The error is in that folder.
(Hope this helps anyone looking for a solution.)