There seems to be some kind of "state" in which some actions will cause chunks to be reloaded and/or a sudden drop to 0 fps and back up (lag spike). For a while I was just flying around in the nether getting frustrated at what seemed like random lag spikes. After I figured out that it wasn't random, I experimented with this for a while and reloaded the chunks. I didn't have the same issue after this.

Actions that cause this:

• Opening chat (T)
• Walking backwards (S)
• Strafing left (A) (This only caused a chunk reload for me.)
• Flying into the world border in the nether. (Not sure if this causes a lag spike directly.)

Known Temporary Fixes:

• Manually reload chunks (F3+A)

To Reproduce this issue:

• Create a new world in single player with creative mode.
• Press F3.
• Try doing the actions listed above.