LTC was doing ~$200,000,000 daily volume back then, nearly same as BTC. Not exactly 'low liquidity.
By now, most litecoin volume does not occur on the OKCoin exchange used by SimpleFX for LTCUSD, not that liquidity is directly proportional to volume anyway. When litecoin used to be at $3 million daily volume even just a month ago, a $200 million volume day for Litecoin is a sign of volatility, not stability.
Litecoin has not had time to consolidate on every exchange at its new price point yet, not that I would count on that happening on OKCoin anyway with all People's Bank of China uncertainties.
In this case, it looks like a whale deliberately dumped and tried to crash the price on OKCoin. Of your plots, the only ones really relevant are your SimpleFX and OKCoin plots. Other exchanges no doubt influenced the recovery indirectly but lack direct relevance to the momentary OKCoin downspike.
There does superficially seem to be deviation between your 5-minute-scale plot of OKCoin futures, versus your 5-minute-scale SimpleFX plot. But it is hard to really conclude much. I know, from other exchange plots unrelated to SimpleFX, sometimes a downspike appearing on a 1-minute plot is reduced on a 5-minute plot's display, and so on. Not all plots are really perfect.
SimpleFX seems to sometimes lag the exchange it is based on by a few seconds, so some weirdness is quite possible. It is not a deliberate scam at all necessarily, though.
Beyond that, I have been using SimpleFX since last year, on many markets, and there is no time for me when they have seemed to deliberately be unfair. So I would be inclined to give them the benefit of the doubt here.
They are offering you 16.6x leverage, they know this is going to wipe everyone out, because the 12% drop @ 16.6x leverage is -200% of your investment!
You choose the size of your positions relative to the amount in your account. Personally, I like the range of options available. Yet I usually deliberately maintain less than maximum-leverage positions even on Bitcoin, and that has far more liquidity than any altcoin.
Just because you can take out up to 16.67:1 leverage doesn't mean you regularly should, outside of brief hyper-monitored trading as a limited portion of a diversified portfolio.
SimpleFX market manipulation is doubtful, judging from my own positive experience, but there is always market manipulation by deliberate whale dumps. For instance, whales will not only do dumps but deliberately yank away giant buy walls just at the moment they are actually needed, potentially on any exchange.