Since Plains of Eidolon launched Dashwire Fishing has been buggy. Nothing has been done about this. You sometimes fall off the Dashwire, you can't cast bait, the fishing spear disappears and Ivara does weird hand movements, and you can't equip the fishing rod while on the Dashwire. Once you fall off the Dashwire you still can't caste bait and have to exit out of fishing then re-enter.