Chunk loading causes excessive tick durations that it can't recover from or takes too long to recover from Waiting for chunk...
With video settings fully max, and render distance 32, go into 1.14 Pre-Release 2 in singleplayer and change to creative mode, fly off into a direction up in the air. After a while chunks will not load, it will fall behind. Tick durations will increase, to around 100ms +. When setting is set to graphics: fast, durations can increase to as much as 500ms + average. And don't seem to come back down or take a long time to catch up. This causes entities to studder because of the high tick duration.
Compare this to 1.13.2 in singleplayer and do the same. Tick durations might ocassionally spike, but always seems to recover. Even though chunks are not all loaded, and it continues to load chunk, the tick durations do not fall behind.
NOTE:
I posted this separately since I think it would get lost in other related chunk issues that may or may not be related/resolved.
Please check if that's still an issue for you in the latest 1.14.4 stable release or the latest 1.15 development snapshot.