Brm_multiple - divergent transitions

I fit a multilevel model using imputed data (m = 50, using mice). I use brm_multiple from brms for this because I can simply use the mids object there. Now I get, for example, 4 divergent transitions in one model after the warmup. If I select combine = F in the model and look at the 50 fitted models individually, only some of them have divergent transitions, but most of them do not. My question now is whether this is an artifact of brm_multiple, such as the incorrect R-hat warning, or whether this is something I should be concerned about. There is little difference in the estimates of the models with and without divergent transitions. I have already made the following adjustments:

control = list(adapt_delta = 0.99, stepsize = 0.01, max_treedepth = 15)

Edith: running the model on one combined set only (mice::complete()) with brm does not give any divergent transitions.