Help needed on the following example, a couple issues

server.R

library(dplyr)
library(purrr)
library(shinyBS)

Module.initUI2 <- function(input,output,session) {
  ns <- session$ns
  
  output$ui_test <- renderUI({
    isolate({
      #Second time this was not triggered
      h4('Test Success')
    })
  })
  
  output$ui_statusBar <- renderUI({
    ui <- tagList(
      br(),br(),
      tags$button(id = ns('mb_inputs'),'placeholder')
    )
    return(ui)
  })
  
  react_inputModal <- reactive({
    isolate({
      modal <- modalDialog(title = 'Test', easyClose = T,
                           'Removed',
                           footer = tagList(
                             bsButton(ns('bb_query'),'Load Data')
                           )
      )
    })
  })
  
  #print placeholder btn count, not working
  observe({
    req(input$mb_inputs)
    isolate({
      print(input$mb_inputs)
    })
  })
  
  #Show Modal, not working
  observe({
    input$mb_inputs
    isolate({
      showModal(react_inputModal())
    })
  })
  
  react_src <- reactive({
    req(input$bb_query > 0)
    isolate({
      removeModal()
      dat <- data.frame()
    })
  })
  return(react_src)
}

testUI <- function(id,title = NULL){
  ns <- NS(id)
  content <-   tags$div(id = id, 
                        div(
                          class = "box-body",
                          uiOutput(ns('ui_statusBar')),
                          h2(title),
                          uiOutput(ns('ui_main'))
                        )
  )
}

test <- function(input, output, session,id) {
  ns <- NS(id)
  react_src <- Module.initUI2(input,output,session)
  
  output$ui_main <- renderUI({
    req(src <- react_src())
    isolate({
      uiOutput(ns('ui_test'))
    })
  })
}


shinyServer(function(input, output) {
  output$ui_launchpad <- renderUI({
    isolate({
      tagList(
        uiOutput('ui_call'),
        tags$div(id='placeholder')
      )
    })
  })
  
  output$ui_call <- renderUI({
    isolate({
      tagList(
        bsButton('cmb_modules','Call')
      )
    })
  })
  
  observe({
    req((val <- input$cmb_modules) > 0)
    isolate({
      uid <- paste0('test',val)
      
      callModule(test, uid,id = uid)
      ins <- testUI(uid,title = uid)
      
      ui <- insertUI(
        selector = paste0('#placeholder'),
        where = 'beforeEnd',
        ui = ins
      )
    })
  })
})

ui.R

library(shiny)

shinyUI(fluidPage(
uiOutput('ui_launchpad')
))