if autoclose is enabled, TTMSFNCTaskDialog needs the timer to be disabled before closing because timer event can fired after object is destroyed.
file fmx.TTMSFNCTaskDialog, line 2417 should be:
procedure TTMSFNCTaskDialogForm.DoResult(AModalResult: TModalResult);
begin
if not Assigned(FTaskDialog) then
Exit;
if assigned (FTimer) then FTimer.Enabled:=false;
if Assigned(FTaskDialog.OnDialogResult) then
FTaskDialog.OnDialogResult(FTaskDialog, AModalResult);
end;