title: group_by and summarise previously (10 minutes ago) worked on my data frame but no doesn't
body: <p>I have a dataframe I am manipulating that I ran <code>group_by</code> and summarise on a few minutes ago. After a forced restart of my computer (due to company IT) my <code>group_by</code> function no longer works. I have had this error sporadically for the last month or so.</p>
  <p>Here's my code:</p>
  <pre><code>covid_per10k_hosp &lt;- datasetv5_pat %&gt;%
  ungroup() %&gt;% 
  mutate(death2=case_when(death==&quot;deceased&quot;~1, TRUE~0)) %&gt;% 
  group_by(PROV_ID) %&gt;% 
  summarize(n_deaths=sum(death2))
  </code></pre>
  <p>example data:</p>
  <pre><code>PAT_ID    PROV_ID    death
  1         A          deceased
  2         A          alive
  3         B          deceased
  4         B          deceased
  </code></pre>
  <p>Expected Output:</p>
  <pre><code>PROV_ID     n_deaths
  A           1
  B           2
  </code></pre>
  <p>Actual Output:</p>
  <pre><code>PROV_ID    n_deaths
  A          1
  A          1
  B          2
  B          2
  </code></pre>
  <p>Edit to respond to comments suggesting additional information, here is the output from <code>sessionInfo()</code></p>
  <blockquote>
  <pre><code>R version 3.6.0 (2019-04-26)
  Platform: x86_64-w64-mingw32/x64 (64-bit)
  Running under: Windows 10 x64 (build 18362)
  </code></pre>
  </blockquote>
  <pre><code>Matrix products: default
  
  locale:
  [1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United 
  States.1252   
  [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
  [5] LC_TIME=English_United States.1252    
  
  attached base packages:
  [1] stats     graphics  grDevices utils     datasets  methods   base     
  
  other attached packages:
   [1] finalfit_1.0.2     ggsci_2.9          icd_4.0.9             
  ggpubr_0.4.0      
  [5] readr_1.3.1        vroom_1.3.1        knitr_1.29         
  tableone_0.12.0   
  [9] dplyr_1.0.2        summarytools_0.9.6 expss_0.10.6       
  Hmisc_4.4-1       
  [13] ggplot2_3.3.2      Formula_1.2-3      survival_3.2-3     
  lattice_0.20-38   
  
  loaded via a namespace (and not attached):
  [1] tidyr_1.1.1         bit64_4.0.5         splines_3.6.0       
  carData_3.0-4      
   [5] assertthat_0.2.1    latticeExtra_0.6-29 pander_0.6.3        
  cellranger_1.1.0   
   [9] pillar_1.4.6        backports_1.1.7     glue_1.4.2          
  digest_0.6.25      
  [13] RColorBrewer_1.1-2  pryr_0.1.4          ggsignif_0.6.0      
  checkmate_2.0.0    
  [17] colorspace_1.4-1    htmltools_0.5.0     Matrix_1.2-17          
  survey_4.0         
  [21] plyr_1.8.6          pkgconfig_2.0.3     broom_0.7.0         
  haven_2.3.1        
  [25] magick_2.4.0        purrr_0.3.4         scales_1.1.1        
  jpeg_0.1-8.1       
  [29] openxlsx_4.1.5      rio_0.5.16          htmlTable_2.0.1     
  tibble_3.0.3       
  [33] generics_0.0.2      car_3.0-9           ellipsis_0.3.1      
  withr_2.2.0        
  [37] nnet_7.3-12         cli_2.0.2           magrittr_1.5        
  crayon_1.3.4       
  [41] readxl_1.3.1        mice_3.11.0         fansi_0.4.1         
  rstatix_0.6.0      
  [45] forcats_0.5.0       foreign_0.8-71      rapportools_1.0     
  tools_3.6.0        
  [49] data.table_1.13.0   hms_0.5.3           mitools_2.4         
  lifecycle_0.2.0    
  [53] matrixStats_0.56.0  stringr_1.4.0       munsell_0.5.0       
  cluster_2.0.8      
  [57] zip_2.1.0           packrat_0.5.0       compiler_3.6.0      
  rlang_0.4.7        
  [61] grid_3.6.0          rstudioapi_0.11     htmlwidgets_1.5.1   
  tcltk_3.6.0        
  [65] base64enc_0.1-3     boot_1.3-22         gtable_0.3.0        
  codetools_0.2-16   
  [69] abind_1.4-5         DBI_1.1.0           curl_4.3            
  R6_2.4.1           
  [73] gridExtra_2.3       lubridate_1.7.9     utf8_1.1.4          
  bit_4.0.4          
  [77] stringi_1.4.6       Rcpp_1.0.5          vctrs_0.3.2             
  rpart_4.1-15       
  [81] png_0.1-7           tidyselect_1.1.0    xfun_0.16          
  </code></pre>