During navigation I've run into a lot different errors and warnings. I copied some of the frequent ones here:
What I found in common from these problems is that they all have something to do with information loss in the update cycle of different parts of navigation. And this could be caused by computer not having enough processing power for the desired update frequency, which is actually not high at all, like the 1.0000Hz and 5.0000Hz in the warning messages above.
Then I found that the laptop's both CPUs' usage is nearly at 100% during navigation. I checked each node one by one. Rviz is very CPU-hungry, when running navigation and rviz together, the CPUs will have nearly 100% usage. But we can avoid using rviz once we have fiducial working. Besides Rviz, several custom nodes made by us are also very CPU-hungry.
For now, we are using Dell 11 inch laptop as the onboard computer for Turtlebot. The situation might not be the same if more powerful devices are used. However, generally speaking, in our custom nodes we should avoid pulishing/updating with a frequency that's too high.
Also please remember to check CPU usage if you find these errors and warnings again during navigation.