[R-sig-ME] glmmTMB false convergence

[Ben Carlson]

Hello,

I'm experiencing an issue with glmmTMB and I can't figure out how to
troubleshoot it. I'm running a model according to Muff et al. 2018:
https://www.biorxiv.org/content/10.1101/411801v2

I have movement observations of multiple animals for multiple breeding
seasons (several thousand observations per animal per year, over 3 years),
and I would like to allow each animal to have a different slope for each
breeding season. This is so that I can test hypotheses regarding responses
to habitat variables among individuals and stability within individuals
across years. "pct_tree" is the habitat variable, representing the
percentage of tree cover.

I'm sorry I can't create a reproducible example, but I don't think I should
post my data to a public forum. Any pointers to how I might troubleshoot
this issue would be very helpful!

I'm running the following model:

TMBStruc <- glmmTMB(y ~ pct_tree + (1|stratum) + (0 + pct_tree |
individual_id:year),family=poisson,data=ssf,doFit=FALSE)
TMBStruc$parameters$theta[1] = log(1e3)
TMBStruc$mapArg = list(theta=factor(c(NA,1)))

The model runs, but I receive the following warning message. Based on the
message, I'm not sure if I should trust my results:

Warning message:
In glmmTMB:::fitTMB(TMBStruc) :
  Model convergence problem; false convergence (8). See
vignette('troubleshooting')

I have searched around but I can't find any information regarding "false
convergence" (including the troubleshooting vignette!).

Please let me know if I can provide any additional information. Thank you
for your help!

Ben

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