Customer upgraded JUNOS to 21.2R3-S7, which has PR1743031 fix for the similar MSPMAND core dump, but still saw mspmand core dump when issuing "show services sessions service-set <>" in a scaled setup. Below syslogs can be seen:
fpc5 ms-5/0: Transient flow-control asserted by XLP MAC over link 2 for 4 seconds
fpc5 ms-5/0: Transient flow-control asserted by XLP MAC over link 3 for 5 seconds
fpc5 Prolonged flow-control asserted by MAC on ms-5/0, bringing interface down
fpc5 ms-5/0: MAC stuck, trigger coredump via nmi
mspmand core dump when running "show serivce sessions service-set <>"
Customer should upgrade to PR1812151 fixed JUNOS release to have a complete fix for PR1743031.