Issue with shinydashboard - dashboardSidebar and dashboardBody - r

Question

I am new to Shiny and Shinydashboard. Please consider the following code snippet (small part of huge code):
dbsidebar <- dashboardSidebar(
sidebarMenu(
menuItem("Dashboard", tabName = "dashboard", icon = icon("dashboard")),
menuItem("Rank List", icon = icon("th"), tabName = "Widgets1", badgeColor = "green"),
menuItem("Build Your", icon = icon("th"), tabName = "Widgets2", badgeColor = "green"),
menuItem("Groups", icon = icon("th"), tabName = "Widgets3", badgeColor = "green")
)
)
dbBody <- dashboardBody(
tabItems(
tabItem(tabName = "dashboard",
fluidRow(
#Pie Charts
splitLayout(
#cellWidths = c("50%", "50%"),
style = "border: 1px solid silver;",
cellWidths = 450,
cellArgs = list(style = "padding: 6px"),
plotlyOutput("Piechart1", width = "400px", height = "200px"),
plotlyOutput("Piechart2", width = "400px", height = "200px"),
plotlyOutput("Piechart3", width = "400px", height = "200px")
)
)
),
tabItem(tabName = "Widgets1",
#Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
sliderInput("TCScore","TCScore:",min = 0, max = 100, value = c(0,100))
),
# Show a plot of the generated distribution
mainPanel(
tabPanel("Heading", plotlyOutput("tbTable"))
)
),
downloadButton('downloadData', 'Download')
),
tabItem(tabName = "Widgets2", "XX"
# #Data Table
# sidebarLayout(
# sidebarPanel(
# sliderInput("TCCScore","TCCScore:",min = 0, max = 100, value = c(0,100)),
# ),
#
# # Show a plot of the generated distribution
# mainPanel(
# tabPanel("Heading", dataTableOutput("tbTable1"))
# )
#
# ),
# downloadButton('downloadData', 'Download')
),
tabItem(tabName = "Widgets3", "third"
)
)
)
On the dashboardSidebar, I have added 4 tabs - dashboard, Widget1, Widget2, Widget3. Initially for each of these tabs, I used simple text to render the UI dashboardBody and I got the display correctly. I started filling in each of these sections - "dashboard", "Widget1" and the display worked correctly for me. Unfortunately, for "Widget2 - when I removed the "XX" and uncommented the code shown above, the UI got completely distorted. It looks like the main UI elements in the dashboardBody did not get rendered? Can anyone tell me what I am doing wrong? Please help. I am sorry I have not posted the entire working code, but it is far too long, hence I had to put up only a small code snippet.
Thanks in advance! Cheer!