When using Chrome or Edge, the scroll bar between the tree and message body will suddenly disappear. When it does and you scroll on the message reply, the tree section (left side) also scrolls. This doesn't seem to exist in Firefox though.

Hmmm... haven't seen that behavior and haven't heard a complaint from anybody else either.

Can you capture a screen cast and post it somewhere to see what's happening?

I use this MB everyday with Edge (Chromium) or other Chromium browser on various platforms (Win, Mac and Ubuntu) and I have not seen what you describe.

REsizing the window to a small width will collapse the sidebar, but it shouldn't affect scroll behavior. I have seen something close to this on iOS with Safari but there it's due to focus issues generally.

+++ Rick ---

Here's 2 video from my dropbox. One is captured in Chrome and the other one is in Firefox. The issue is happening as well in Edge browser. Video capture

Sorry for not getting back - I missed this message...

Looked at your video and the behavior you see is normal.

Firefox can't render custom scrollbars so you get those fat ugly scrollbars on the window.

Chromium browsers will render a 'skinny' toolbar which is styled to be very slim by design - but it's definitely there.

The landing page showing items is actually not coming from the same site, so that's why the styling doesn't match - it has a regular scrollbar on the inside frame.

The other pages use the custom message board scrollbar styling.

+++ Rick ---

Getting back to this as I started running into this as well. Turns out this is caused by the Google Ads running here which modify the server rnedered document behavior. That's seriously screwed up.

Google changes the layout by adding and auto height to the flex container that contstrains the size of the list and the content so it can scroll:

<div class="flex-master"  style="height: auto !important">

By doing that it forces a top level browser document scrollbar which accounts for the missing scrollbars in the content you're seeing.

Removing the ads makes this work correctly. The reason I didn't see it is because my ad blocker blocked the ad scripts from loading 😃

I added a fix which is to basically reset the tag with:

setTimeout(function() {
    $(".flex-master").attr("style","")
},800);

This works, but it's ugly in that it jumps the initial render a bit. Worse google checks for the scrolled content region and puts it back on each of even the Ajax loaded navigation content. It's almost sinister...

Anyway - added the above code in a couple of areas related to navigation and that should take care of it. The scrollbars now show even when the ads are running in most cases.

+++ Rick ---