While riding a Rhinoceros i can't do a charged shot with a bow

having my own private server with base settings playing on the isle of siptah map.
I’m riding a rhinoceros with savage grey skin and a calvary saddle and do have a Harpy’s bow with razor arrows eqquiped.
When riding the rhino i can fire normal shots but when i’m holding to build up for the charged shot and waiting for the arrow to shine and fire after that i get a normal shot instead of a charged shot.
With the exact same gear on a white horse with potian warhorse saddle the charged shot does work as its supposed too.
When riding a normal Rhinoceros with war saddle the charged shot also doesnt work.
so it has something to do with the Rhino and the bow in combenation.