'Show heartbeats' output may indicate heartbeats from modules to CPM are being lost even if heartbeats are not currently being lost. The fix is available in XOS 9.7.1 or later.
The 'show heartbeat' output on the chassis show that the link quality from other modules to the CPM(s) is not at 100%.
Here is an example of 'show heartbeat output for link quality to CP1 and CP2:
Link Quality TO slot(module): 13(cp1)
FROM 1 2 4 5 6 7 8 9 10 11 13 14
ON ports
CB A: 093% 100% 100% 100% 100% 100% 100% 093% 100% 100% NA 093%
CB B: 093% 086% 100% 093% 100% 093% 093% 100% 100% 100% NA 100%
DP A: 100% NA 100% 100% 100% 100% 100% 100% 100% 100% NA NA
DP B: NA 100% 100% 100% 100% 100% 100% 100% 100% 100% NA NA
DP C: NA NA NA NA NA NA NA NA NA NA NA NA
DP D: NA NA NA NA NA NA NA NA NA NA NA NA
Link Quality TO slot(module): 14(cp2)
FROM 1 2 4 5 6 7 8 9 10 11 13 14
ON ports
CB A: 093% 093% 100% 100% 093% 100% 100% 093% 093% 100% 100% NA
CB B: 100% 093% 093% 100% 100% 093% 100% 100% 100% 100% 093% NA
DP A: NA NA NA NA NA NA NA NA NA NA NA NA
DP B: NA NA NA NA NA NA NA NA NA NA NA NA
DP C: NA NA NA NA NA NA NA NA NA NA NA NA
DP D: NA NA NA NA NA NA NA NA NA NA NA NA