I just came across this issue after using the flogger node in "Select Object mode" then switching back to "Full Message Object". The "red triangle of doom" appears and will (sometimes) go away, and sometimes not. It's random.
Running latest everything on Raspbian. While no big deal to fix (delete node and start again), maybe the author? may wish to take a look.
It would probably help to be explicit about which node you are actually using as there are 3 listed on flows.nodered.org
Though given none of the 3 have been updated in over 6.5 years you may be out of luck with any of the authors being interested in fixing things. 2 of them are forks of the original.