Some Esperanto verbs are both transitive and intransitive!
In Being Colloquial in Esperanto (also available at ELNA), David K. Jordan lists the following...
Another verb of interest is fajfi, to whistle. PIV1 defines it as intransitive, while PIV2 defines it as transitive, both using the same Zamenhofian example: li mallaŭte ekfajfis la arion de Kalĥas! My 1980 edition of the PV defines it as both transitive and intransitive.
And then there is pardoni. Some deem it intransitive, others transitive. And if transitive, just what kind of direct object does it take? Think about a sinner and a sin. Examples, even from Zamenhof, show indecision as to whether the sinner or the sin should play the role of direct object. English suffers the same problem, with words like pardon and forgive. (Esperanto's ability to substitute trailing -n for prepositions complicates things a bit. I've seen some pardoni-examples in which both sinner and sin had -n ((at least) one must be prepositional, but which?), some in which only one did (accusative or prepositional?), and some in which neither did (making pardoni intransitive... or does it?).)
When I was proofreading Robinsono Kruso (Pastro Krafft's translation of Robinson Crusoe) for Project Gutenberg, I was struck by the frequent use of words formed according to the model preposition + noun + -n, used adverbally. This is a legal construction (See Butler's description of the accusative of direction in Step by Step in Esperanto, § 442) but it is not often used today, probably due to parsing difficulty. Not only does it lump together all the components into one package having the appearance of a noun in the accusative, it also requires that the reader know the transitivity of the relevant verb before the meaning of the -n can be determined. (It's much easier to read if that preposition is kept separate; there are far fewer prepositions to learn than verbs, and few of them indicate motion in themselves.) Verbs of indeterminate transitivity make parsing even more difficult!