You can install a cable or chain above the top rung of the ladder to help it sit on trunks and palms ... that's what I did.
The bugger comes when the trunk dia is just too fat for the ladder or the size where the ladder gets jammed.
After I fell when the ladder slipped I gave it away, the feet skid off, I was working alone and had it firmly planted (so i thought) but underneath the mulch in the garden was plastic weed mat ... whoosh went the ladder and down I went. Threw the chainsaw away and hit the deck.
So then it either becomes a 2 man op or a lot of stuffing around tying in the ladder, yourself etc ... ahhh, put ya gear on and just climb it. You have to have your gear on anyway.
Also, when cleaning palms many times you have to then put the ladder the other side of the palm to get the crap around the back. Also, when there are heaps of dead butts that are still attached you put the ladder on the trunk, go up, pull butts off, come down, raise the ladder another couple of rungs, go back up and sometimes have to do the same again ... PITA.