On low storage space, macOS may choose to shut down the app: If the remaining storage space on your system volume group becomes so low that the operating system considers it to be critical, macOS versions as of 10.15 or higher will generate a system-wide cache-deletion warning status. As a side effect, this can send termination signals with the internal code “BADDD15C” (“bad disk” in Leetspeak) to running apps, including System Monitor. This quits the app, so it can no longer monitor free storage space. You can recognize this effect by a message of the following pattern in the system log:
launchd: [gui/UID/application.com.bresink.app.systemmonitor.SN1.SN2 [PID]:] exited with exit reason (namespace: 15 code: 0xbaddd15c) - OS_REASON_RUNNINGBOARD | <RBSTerminateContext| code:0xBADDD15C explanation:CacheDeleteAppContainerCaches requesting termination assertion for com.bresink.app.systemmonitor reportType:None maxTerminationResistance:NonInteractive attrs:[
<RBSPreventLaunchLimitation| <RBSProcessPredicate <RBSProcessBundleIdentifierPredicate "com.bresink.app.systemmonitor">> allow:(null)>
Workaround: This is a known design flaw of macOS. There is no known workaround.
Updated for version 6.5 - 2026–03–24
Statistics for outgoing network data traffic may not work for specific combinations of macOS version and Ethernet chips: The “write” activity indicator, as well as the “outgoing packages” statistics value for certain Ethernet ports used in specific Macintosh models may not work with all versions of macOS. In such a case, System Monitor shows no write activity or zero packages for the affected network interface, respectively. For example, the “Aquantia Aqtion 113” driver of macOS 13 is affected by this problem. It is used by the 10 GBit/s port of the Apple Studio.
Workaround: This is a known defect of older versions of Apple network interface drivers. Upgrade to macOS 26 or later to fix this problem.
Updated for version 6.4 - 2025–11–10
For very narrow menu-bar items, the Liquid Glass feature may cause display errors when the item is selected: macOS 26 introduced a new graphic appearance with glass-like optical effects and strongly rounded corners. Such design effects are also applied when macOS highlights an element in the menu bar after a click, such as a monitor item of System Monitor. If you configure a monitor item to be very narrow, e.g. by just defining a small vertical label as placeholder to hold a menu, with no other display elements in the bar, the Liquid Glass highlight for this item may look wrong. The strongly rounded corners and the reflections can work against each other in this case. For example, a bright grey highlight may turn into a black vertical eye-like shape.
Workaround: This is a known design flaw of macOS 26. There is no known workaround.
Updated for version 6.4 - 2025–11–10