title: Error when estimating CI for GLMM using confint()
body: <p>I have a set of GLMMs fitted with a binary response variable and a set of continuous variables, and I would like to get confidence intervals for each model. I've been using <code>confint()</code> function, at 95% and with the <code>profile</code> method, and it works without any problems if it is applied to a model with no interactions.</p>
  <p>However, when I apply <code>confint()</code> to a model with interactions (continuous*continuous), I've been getting this error:</p>
  <pre><code>m1CI &lt;- confint(m1, level=0.95, method=&quot;profile&quot;)
  </code></pre>
  <blockquote>
  <p>Error in zeta(shiftpar, start = opt[seqpar1][-w]) :
  profiling detected new, lower deviance</p>
  </blockquote>
  <p>The model runs without any problem (although I applied an optimizer because some of the models were having problems with convergence), and here is the final form of one of them:</p>
  <pre><code>m1 &lt;- glmer(Use~RSr2*W+RSr3*W+RShw*W+RScon*W+
   RSmix*W+(1|Pack/Year),
   control=glmerControl(optimizer=&quot;bobyqa&quot;, 
      optCtrl=list(maxfun=100000)), 
     data = data0516RS, family=binomial(link=&quot;logit&quot;))
  </code></pre>
  <p>Does anyone know why this is happening, and how can I solve it?</p>
  <p>I am using R version 3.4.3 and lme4 1.1-17</p>