Add CAN bus utilization noise to known issues (#1713)

* Add CAN bus utilization noise to known issues

* Fix misspelling

Author: PeterJohnson

source/docs/yearly-overview/known-issues.rst

@@ -22,6 +22,13 @@ Game Tools Autorun graphics say 2020
 
 **Workaround:** This can be safely ignored, if the menu item says 2022, you are installing the correct software.
 
+CAN bus utilization is noisy
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Issue:** CAN bus utilization as reported live by the DS or as shown in the DS log has significant variation or "spikes" in the data. This is due to the RoboRIO occasionally counting CAN packets in the incorrect time period, so one period will have a much lower utilization than reality and the next a much higher utilization than reality.
+
+**Workaround:** Zoom in on the DS log plot and look for time periods when the utilization is stable (the spikes will be both above and below this average). The average utilization is the true utilization.
+
 Updating Properties on roboRIO 2.0 may be slow or hang
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^