I’m asking for help for an annoying, (ironically) non-deterministic error when I solve Jumpy-ODE’s (i.e. “Piecewise Deterministic Markov Processes”). It tends to start happening as I increase the number of processes and does not occur for similar smaller systems. or short times.

```
>>> p0 = ... # a jump problem with 128 independent jumps acting on top of an ODE problem of 64 dimensions
>>> out = solve(p0, Tsit5())
ERROR: Tried to add a tstop that is behind the current time. This is strictly forbidden
```

It’s a bit hard to provide reproducing code because of the size of the jump problem that I’ve defined. I can provide code where I define the constantrate jump problem. Not enough to run, just showing how I build the JumpSet.

```
function approx_piecewise_jump_problem(model; tspan = (0.0,1.0), u0 = ones(model.nstates) )
odeprob = theta_ode_prob(model; tspan, u0)
jumps = []
# selection increasing
for i in 1:Int(model.nstates)
# (u+ θ) * σ
rate(u,p,t) = (2*model.Ne*fitness(model, t, i)
# + 2 + sum(mod(u[j],1) - 2*model.Ne*mutation_matrix(model, t, i, j) for j in 1:model.nstates if j != i)
# mutation contribution
) * u[i]
function affect!(integrator)
integrator.u[i] += 1.0
nothing
end
push!(jumps,ConstantRateJump(rate, affect!))
end
# drift decreasing
for i in 1:Int(model.nstates)
rate(u,p,t) = floor(u[i])*(sum(u) - 1 )
function affect!(integrator)
integrator.u[i] += -1.0
nothing
end
push!(jumps,ConstantRateJump(rate, affect!))
end
jset = JumpSet(; constant_jumps=jumps)
return JumpProblem(odeprob, Direct(), jset)
end
```

The underlying ODE is a well behaved quasi-linear problem. (You can tell by my `2*model.Ne`

that I am doing population genetics.)

Googling this error only yields some issues with thread safety in ensembles, but I’m only single threading for now. The stack trace is the usual unhelpful ODE type dumps, but hits the relatively standard code in the Gillespie thingy.

```
1. error(s::String) at error.jl
2. add_tstop!
3. register_next_jump_time! at ssajump.jl
4. AbstractSSAJumpAggregator at ssajump.jl
5. apply_discrete_callback! at callbacks.jl
6. handle_callbacks!
7. _loopfooter!
8. loopfooter
9. solve
```

Should I file an issue, or is a problem on my end? If it’s a `DifferentialEquations.jl`

issue, can anyone think of a workaround in the meantime (alternate sovlers maybe?) while I come up with an MRE for what seems to be a subtle issue?