Lag isn't always a network problem. In flash games, flash rendering is a big problem too. For this game in particular, whenever a chase chain happens, there will be delays. Because on the server side, chase takes almost no time, whereas... well.. chase takes however long it does to render on client side. So whenever a mystery is to be cast in the middle of the round, especially after a chase chain have occurred, there would be a difference in when you think you casted it and when it is actually casted.

I'm not sure about attack/mystery animation, as those tend to be shorter and usually lead into a chase themselves which masks the problem. But it's possible that long-animation mystery, such as Kazekage gaara, might also cause this problem if the server only allot a fixed amount of "wait time" for each mystery cast.

This, by the way, is why I mentioned hardware on the lag issue. Because different computer hardware will render things at different rate on flash. I know there is a slight difference at which I can retreat from fox to complete all my attacks between my weaker laptop vs my desktop (thou slight, because my weaker laptop is still a decent machine. But, from what I've heard, chrome book is horrible on this front)

It doesn't have anything to do with whether it runs "smoothly". a 8-chain chase, for example, would take 5-8 seconds to render (depend on the chase and what started it). But on the server end, only about 1-2 second is given before the battle ACTUALLY proceed to the next step. So at that point in time and thereafter, what you see happening will be 1-3 seconds behind what is actually happening. It does self-correct somewhat thereafter, as the server 'waits" for a finite amount of time after each step, and if you are behind but is faster than the time it waits for, you will catch up a bit. But by and large, you will be behind.

This "part" of the problem have always been there. But it could be unnoticeable depending on how your team works and whether you have other problem. (Delay of 1 second might be bad, but if it's the only delay, you might not notice it. But put it on top of another two 0.5s delays, it might suddenly become noticeable. Also, some teams don't rely on middle-of-round casting so none of the delay ever really applied to them)

Also, if you play a 60 fps movie @50fps, that would be smooth too. Just because it's smooth doesn't mean it's not lagging.

The mod did suggest you to clear cache, I would too. Because excessive cache, among other things, can cause flash render slowdown.

On that note, there are a number of software reasons why there might be slowdown, including previously healthy software that randomly decided to become a bloatware or even anti-virus running on the back ground. "Hardware haven't changed" doesn't really mean much unless you have excessive hardware such that such changes shouldn't impact you. (check your resource manager, if any one of your core/thread is over 70% usage, you might have a resource race on your hand)

And finally, Murphy's law and the law of small numbers. There are MANY factor that might impact the game. Quite frankly, sample size of less than 10 players over a duration of less than a week is meaningless and pretty useless for diagnostics.