Answer by starja for shiny module with observeEvent updates based on previous inputs

Below is a solution that works. The problem was that you nested your observeEvent in the module. I'm not entirely sure why this led to problems, some values weren't processed correctly. However, you don't need to nest the observeEvent, the second one gets also triggered by the actionButton in the modal when it is by its own. Additionally, I included a removeModal before the success notification is shown:

library(shiny)library(shinyWidgets)library(shinydashboard)ui <- navbarPage('page', collapsible = TRUE,  tabPanel("test",           useSweetAlert(),           sidebarLayout(             sidebarPanel(),              mainPanel(               uiOutput('all_products_ui')             )           )  )) # end navbarserver <- shinyServer(function(input, output) {  list_products <- c(1,2,3,4,5)  # Now, I will create a UI for all the products  output$all_products_ui <- renderUI({    r <- tagList()    progress_move <- 0    for(k in 1:length( list_products )){      r[[k]] <- ExistingProductUI(id = k, product = list_products[[k]] )     }    r  })  # handlers duplicate a call to module depending on the id of ExistingProductUI   handlers <- list()  observe(    handlers <<- lapply(seq.int(length( list_products )),                         function(i) {                          callModule(ExistingProductUpdate,                                      id = i,                                      product = list_products[[i]] )                        })  )    handlers}) # end of server ---- # UI module ------------------------------------------------------ExistingProductUI <- function(id, product){  ns <- NS(id)  box(title = as.character(product),       product,       footer = tagList(        actionBttn(          inputId = ns("change_selected"), label = "change"),      )  )}# server module ------------------------------------------------------ExistingProductUpdate <- function(input, output, session, product){  ns <- session$ns  observeEvent(input$change_selected, {    # when box button is clicked for this product (id)    # FIRST: show a modal    showModal(      modalDialog(        title = "what do you want to change?",        tagList(          radioGroupButtons(inputId = ns("change_selected_choice"), label = "change x", choices = c(1,2,3,4)),          sliderInput(ns("change_selected_pct"), "change y:", min = -50, max = 100, value = 0, step = 5)        ),        easyClose = TRUE,         footer = tagList(          actionButton(ns("change_selected_submit"), "submit!", icon = icon("check")),          modalButton("never mind")        )      )    )  })  # SECOND: when change_selected_submit is clicked,   observeEvent(input$change_selected_submit, {    # do some calculations with product using what I inputed in modal ---     # then, update a table ----     # functionToUploadThings(product, input$change_selected_choice)    # THIRD: Close with a confirmation    removeModal()    sendSweetAlert(      session,      title = "Success!",      type = "success",      btn_labels = "Ok",      closeOnClickOutside = TRUE,      width = NULL    )  }) }shinyApp(ui, server)

Please note: I made some modifications to make your MWE work:

• include library(shinydashboard)
• p$title and product["title"] to product
• change labels to label in radioGroupButtons
• comment out functionToUploadThings(product, input$change_selected_choice)

Edit

I'm still not super sure what happens when nesting the observeEvents. I made a small toy example and played around with the reactlog. It seems that nesting the observers generates a new observer for button2 every time button1 is clicked. These observers are not removed and lead to unwanted behaviour. In contrast, when using separate observeEvents, the observer for button2 is only created once.

library(shiny)library(reactlog)ui <- fluidPage(  actionButton("button1", "click"))server <- function(input, output, session) {  observeEvent(input$button1, {    print("from first observer")    print(input$button2)    showModal(      modalDialog(        title = "what do you want to change?","some text",        easyClose = TRUE,         footer = tagList(          actionButton("button2", "submit!", icon = icon("check")),          modalButton("never mind")        )      )    )    # nested observer -> leads to remaining observers    observeEvent(input$button2, {      print("from second observer")      print(input$button2)      removeModal()    })  })  # independent observer -> generates only one observer  # observeEvent(input$button2, {  #   print("from second observer")  #   print(input$button2)  #   removeModal()  # })}shinyApp(ui, server)