I have had some trouble with a conveyor delay in a model.
I know how to construct one with an inflow, an outflow (where the delay conveyor function nests) and a loss outflow. Here I have three separate outflows with respective delay conveyor functions and no loss outflow, since technically there are no losses. Currently I simply have the same function in all three outflows, with weights applied to them (all adding up to 1) and 0 for the loss rates. Funnily enough the stock goes negative. It is not due to initialisation either, since the delay time is significantly shorter (1/40) than the model run time and the stock just keeps draining at the same rate throughout the run.
Unfortunately I may not post the model but could do a simplified version. I simply remodelled it (closely along the lines Bob described) to get rid of the problem for now