Based on the recommendation of PhotoEngineer I started presoaking my film before pouring the first dev. I have so far not encountered any problems with presoak. It actually makes me more comfortable, as the first three or four batches of water take on some strong color from the film (blue or orange depending on make) which I am happy not to get into the film chemistry.
As for your Jobo troubles: I have no idea how this could have happened, I've used the Jobo 1510 and the 1520 for years now with only neglectable leakage. I'd treat it as a freak incident until it happens another time at which point it may be advisable to change the dev tank just in case. From reading what you did everything seems correct.