RES ERROR <-4> means in INDI that there was a timeout. AP says in the protocol description that :MS# has not been accepted. Under these circumstances the controller does not send a response, hence the timeout.
I then checked if the controller is in parked or slewing status. That was not the case.
LX200AstroPhysicsExperimental::updateTime entry
I'll look at that tomorrow because I did not find any traces that method UnPark has been called.