title: LME4-GLMER - PROBLEMS WITH ALLFIT. Mismatch between summary(allFit(model)) and summary(model)
body: <p>I'm writing to ask a question about the <code>allFit</code> function of the <code>lme4</code> package.</p>
  <p>I have raised a GLMM, with the following structure:</p>
  <pre><code>MM &lt;-glmer(y~ x1 + x2 + x3+x4 + (1 | subject)+(0+x1+x2|school), data=data, family =poisson(), offset=log(n))
  </code></pre>
  <p>I can't offer the original data, but suppose:</p>
  <ul>
  <li><code>x1</code>,<code>x2</code>,<code>x3</code>, <code>x4</code> are the auxiliary variables.</li>
  <li><code>y</code>: response variable</li>
  <li><code>subject</code>: represents each row of the data frame</li>
  <li><code>school</code>: represents groups of rows of the data frame.</li>
  <li><code>n</code>: sample size</li>
  </ul>
  <p><strong>Therefore, I have a GLMM model, with a random intercept and two random slopes that are also correlated with each other, but without correlation with the intercept.</strong>
  When I perform simulations, on some occasions, convergence warnings are given.
  I have made a review of all available documentation and related questions. Specifically, looking at the <a href="https://cran.r-project.org/web//packages/lme4/lme4.pdf" rel="nofollow noreferrer">latest <code>lme4</code> documentation</a> (page 16), to further investigate these warnings, I used the allFit function .
  The results show me that no optimizer, or only occasionally the L-BFGS-B, gives problems, and that all the parameter estimates, both for the fixed and random effects, are practically the same.
  However, <strong>I don't understand why, when these models have convergence warnings, the results I get by doing the variance-covariance matrix and the summary on the model are completely different from those returned by the summary function on the object resulting from applying <code>allFit</code>.</strong></p>
  <pre><code>beta &lt;- fixef(MM) differs noticeably from summary(allFit(MM))$fixef
  
  var &lt;-as.data.frame(VarCorr(MM))$sdcor differs noticeably from summary(allFit(MM))$sdcor
  </code></pre>
  <p>Being the values ​​returned by <code>summary(allFit)</code> consistent with those deduced from the sample.</p>
  <p><strong>I have verified that when the model shows no convergence problems, the results of <code>fixef(MM)</code> and <code>VarCorr(MM)</code> exactly match those returned by <code>summary(allFit(MM))</code>.</strong></p>
  <p>I have performed the test in the latest available update '1.1.29' and in '1.1.28', and the same thing happens to me in both.</p>
  <p>I'm sorry I can't provide the dataset, and I apologize in advance if this has already been asked, because I've searched a lot but didn't find this bug.</p>