You get in trouble when you hit the word “yet.” That implies a sort of “time space” into which time units are being created one at a…uh…time.
There’s not enough information to know what would happen here. I mean, yes, it’s a paradox, because time travel into the past is always a paradox: there are now two versions of the past: one containing the future traveller’s experiences, one not. You don’t have to go on a patricidal murder spree or anything.
But the root of your question depends on the part you didn’t answer:what happens to “time units” as they become the past? If there’s a big metaphorical box of them somewhere (so that from 2016, the time unit of 1986 still “exists”), and you’re jumping to it, than the 1986 you’re going to clearly isn’t the same one you lived through before. In this “time space” the box of expired units exists, and in the old one it didn’t. So it’s probably not just a paradox, but one resolved by a multi-world explanation.
Alternatively, you can argue that travel through the “time space” container to a previous point effectively ‘resets’ that point, and you’d be back where you were (although still with an extra “you” creating a paradox) with the future not existing yet. From the “container” side, all times exist, but from the “world” side, time units in the future are inaccessible/nonexistent.
Luckily (and as you can tell from my username, I’m an expert at this), your whole explanation is wrong and spacetime is fully extant at all times, although travel along certain dimensions is limited to a single direction for most particle types. The Dromidians set it up that way, and anybody that messes with them ceases to exist.