I've got this happening also. Started when I upgraded to 1.4.0. By the 3rd layer it's almost a whole layer behind. Tried increasing the size the file in the settings to 30mb, and I only have it using: Sync with job progress, Center viewport on model, Show moves, Show retracts, Show approx. print head position. Everything else is not checked. That appeared to be the minimum amount of information to be able to see what was actually happening. Before the upgrade it kept up, afterwards it no longer did. Running on a Pi 3B (not plus) with a touch screen attached, but screen is in blank mode most of the time, and am using a hard wired connection to my network, so WiFi Lag should not be an issue. Not seeing any errors in any of the logs for octoprint (looked directly at them via PuTTY SSH and tailed them while running a print. Average CPU load while printing is under 1, so not overloaded either.