x-axis ticks of time-series plots do not display properly

[yepw]

As shown in the above screenshot, "3" and "8" are missing from the x-axis.

How to reproduce:

1. Open the "pick & place - panda" example
2. Create a new time-series graph
3. Drag and drop any joint into the graph
4. Scrub the "end" marker on the timeline bar to display robot motions from 0 s to 10 s
5. The x-axis of the time-series plot display as the screenshot above.