Has it never happened outside of Washington in 2016?
In CA-31 in 2012, there was a R-R duel despite Democrats getting 48.5% in the primary. (seat was gained in 2014 and voted for Obama by 16 points and Clinton by 21)
And TBH there was a good reason why it ended up as RvR - both R's were former incumbents who were running against each other because their gerrymanders had been undone by the commission. In general the 'challenging party lockout' that is always hyped up in top two contests is just that - hype. There are a variety of reasons for this: the uber-expensive California media markets shutting down all but the most viable candidates, the strength of the dem party ending potential primaries before candidates enter, and press awarding credibility to a few(sometimes if any like CA45 right now) candidates on both sides. Another feature of California is its shear size, and the shear size of the parties. Most people say endorsements don't matter, but when you open your CA voter information guide and there's an entire page listing endorsements from various prominent CADems, the quantity is often enough to convince the voter who is removed from politics until the final moment.
Now, so far the top two is not just fine but works in everyones favor because it only is implemented in safe states. However, there is a 2020 ballot initiative to implement it in Florida, and I can see a bunch of problems ensuing there. Weak parties, tribal politics, a multitude of competing factions in both parties, constant 50-50 races...its a recipe for disaster no matter if you support the GOP/Dems.
