That is a problem with your device.

It seldom happens to me, but does occasionally - when it does I notice the PC is under high load levels. (Seen in Task Manager.)

I'll assume windows then. When it's jerky, does task manager show unexpectedly high CPU or memory usage?

If you close all other running programs does the performance change?

If you use wi-fi, does using a hard connection change anything?

[Nice thing about the above is few simultaneous changes to sleuth out the cause and effect.]

My barometer for game performance is the spinning coin in the bank icon, top right. [Sometimes windows goes stupid, getting or installing updates usually, and the coin stops spinning. I know at that point to walk away, things aren't going to be playable. Most of the time the coin resumes spinning after a few minutes and I get on with things. Other times the browser errors out and I just hit F5 to refresh. Rarely things are worse, and I get out of all Chrome windows [all browsers are buggy and have memory leaks - you have to get out of all windows for it to start fresh]. Even more rarely I have to restart the machine [same issue].

Don't forget - you want to hit F5 every day at 00:00z (UCT+0) [z=zulu], and again at 2 - 2.5 hours later - the first to effect the new day's bonuses (e.g. -10% stamina depletion), the latter to effect the new day's varmints. (e.g. the new day's Battling Assailants miscreant.) Similarly, if you're chasing varmints, finish chasing them by 00:00z - they can disappear on you while you're killing them. [Deeply irritating on Alpha's when this happens.]

If you think about it / my best guess is, the servers have to constantly update your machine with the position of everything on it. So, for example, a march may have boosts applied to it, so the servers must (I suspect) continually send to your machine where the march is now. If your net connection is poor, I suspect the rate of position updates and displays gets slower, and you see the jerkiness you notice. [So watch the coin spin rate?]

GL&HF