Brms: How to simulate runtime and convergence issues?

I need to give students a practical session on solving runtime and convergence issues using simulated data. However, how to simulate these warnings one by one?

Data: 100 individuals, 70% female and they are 10 years younger than males (this can be changed however needed)

data = bind_rows(
 tibble(sex = rep("Female", length.out = T), age = rnorm(70, 40, 4)),
 tibble(sex = rep("Male", length.out = T), age = rnorm(30, 50, 4)))

m = brm(age ~ sex, data = data)


How should I edit the simulated data and/or model so that it starts showing

  1. high Rhat values or
  2. low Bulk_ESS or
  3. low Tail_ESS or
  4. divergent transitions?

Your help would be much appreciated!