Comment 10 for bug 1959747

ya I'm seeing this also. Thunderbird hangs for a few seconds when selecting an email and scrolling down the body. It happens initially then seems to be ok. It's almost reproducible... just click on another email, click back to the original, and try scrolling down. Do this until it occurs again. This also triggers an error:

IPDL protocol error: Handler returned error code!

###!!! [Parent][DispatchAsyncMessage] Error: PClientManager::Msg_ExpectFutureClientSource Processing error: message was deserialized, but the handler returned false (indicating failure)

Other errors include:

ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load

(xfce4-panel:659): xfce4-panel-CRITICAL **: 18:26:19.276: panel-window.c:2391 (panel_window_active_window_geometry_changed): expression 'WNCK_IS_WINDOW (active_window)' failed.
JavaScript error: resource:///modules/AddrBookCard.jsm, line 166: NS_ERROR_NOT_AVAILABLE: PreferDisplayName: undefined - not a boolean

The later actually causes my display to go black for a few seconds!!! Could be unrelated, but only happens when launching thunderbird. Effects v91.1.0 and up.