CoinLenders called "make a transaction" to Inputs, but Inputs was under DDoS at that time. CoinLenders didn't know if it went through or not, and it's better to be safe than sorry, so a manual processing was required.
Thanks for explanation, TradeFortress. Is there anything like two phase commit protocol implemented between coinlenders and inputs.io nodes? From your description of failure it doesn't seem. I suggest you to use It, although it may decrease performance of both sides, but will increase security for sure. In this case transaction would be rolled back on coinlenders side after some timeout, followed by appropriate message in application like "try again later".
The other thing you may try is not to use the same route from coinlenders <-> inputs.io communication as you use for coinlenders <-> outside traffic and inputs.io <-> outside traffic. This way you would avoid congestion if any of 2 is under DDoS from outside, assuming that you have some inverse proxies (like nginx) in front of your servers that keep applications from excessive load.
Just my 2 cents... Good luck.