"Error: invalid 'labels'; length 17 should be 1 or 16"

[MaxAlex]

Describe the bug
After importing data on a 17-fraction experiment, all result windows show only the message "invalid 'labels'; length 17 should be 1 or 16"; see screenshots below. I tried removing one file (which didn't fit the same fraction-labeling scheme as the rest) and the error changes to "invalid 'labels'; length 16 should be 1 or 15."

The Rstudio console tab shows several instances of the error:

Warning: Error in factor: invalid 'labels'; length 16 should be 1 or 15
  154: <Anonymous>
  153: stop
  152: r
  151: eventReactiveValueFunc
  107: data
  100: .validate [modules/005_Summary/summary_005_maxquant.R#9]
   99: module$plot_func [modules/005_Summary/summary_005_maxquant.R#18]
   97: renderText [server/build_modules.R#112]
   96: func
   83: renderFunc
   82: output$summary_005_maxquant-text
    1: shiny::runApp`

Screenshots

...and so on...

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Firefox and Edge
• Version: 1.0.10

Additional context
This is happening on an Azure VM with a fresh install of R (version 4.2.1) and Rstudio. Shiny is at version 1.7.2 (which auto-installed for DO-MS.)

Let me know if you need any additional details. Thanks!