Around the line 100 of the page 236 of Lingua Latina per se illustrata, there is the sentence
Tum vēro nova et mīra rēs accidit: delphīnus, cantū allectus, repente hominem natantem subiit eumque in dorsō suō sedentem vēxit et in lītore Graeciae salvum 100 exposuit.
Is this sentence we have "repente hominem natantem", which would mean that the action of the verb "subeo" would be applied against the object hominem natantem, implying that the dolphin is riding Aríón which does not make any kind of sense.
Like wise we have "dorsō suō sedentem vēxit" where the verb veho is being used in active form with Arion being the object, thus meaning that the dolphin is riding Aríón.
And so on there plenty of this anomalous phenomena in the entire page 236.