While building nether highways today I noticed when walking/running and placing blocks in front of my character the block place sound will stop, the block place animation will stop, and you can continue to place blocks. Eventually the game catches up and more often than not a good amount of blocks will disappear from under you and return to the inventory. The same thing happens when walking backwards and placing blocks where the placed blocks disappear and return to your inventory.

Similar things happened while mining blocks. The block breaking sound stopped, the axe continued to swing, blocks disappeared as if broken, suddenly the blocks reappeared as if not mined.

I happened to notice mob behavior got a bit wonky when these block lags occurred. Freezing in place, stuttering animation, spinning in circles.

I do have my simulation distance set to 6 chunks and I didn't set it to 4 to see if the issue resolved. I can try that tomorrow to see if it helps.