[R-sig-ME] lmer model converged before, but couldn't now

[Zhaohong Wu]

Dear All,

I fitted a linear mixed effects model using lmer() two weeks ago, and the model was able to converge. I rerun the model over the weekend (two days ago) and now there are warning messages about max|grad| and negative Herssian that the model failed to converge and the t values from the summary of the un-converged model are not the same as those I originally got from the originally converged one. Any idea why this could happen? Is it because of an update of the lme4 package or something?

I saw a post here, http://r.789695.n4.nabble.com/Why-have-my-glmms-stopped-converging-lme4-td4691786.html, where Dr. Ben Bolker suggested that the max|grad| warning are just false positives, but since the un-converged one gives different t-values, I do not know which results I should rely on.

E.maximal.model.RT<-lmer(RT~ 1+A*B*C+(1+A*C|Subject)+(1+A*B*C|Item), data=Edata, verbose=2,control=lmerControl(optCtrl=list(maxfun=50000)))

The DV is a continuous one, and all the three IVs are categorical and sum-coded.

Any suggestions would be greatly appreciated.

Best,
ZW
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