Spatio-tempral Bayesian Poisson model convergence investigation

I am fitting a spatio-temporal Bayesian Poisson model with 22 explanatory variables, an offset variable, 2200 observations and non-informative priors. I am using the package CARBayesST which uses MCMC. I tried different specification for the spatiotemporal effects. With the exception of one of the specifications, I have not been able to achieve convergence. I check that by looking at Geweke's diagnostics and by looking at the trace plots of the coefficients. An example of one of the trace plots follows. I am doing 4000000 sample size, 800000 burn-in, and thin = 10. I started from 500000 with 100000 burn-in and thin = 10. I have been increasing to 4 million but it doesn't seem it is helping with convergence. Should I keep increasing the sample size, or based on the trace plots (they are very similar to the one attached for all coefficients), I should change thin size, burn-in? Is there anything else I need to do?