In V2.0 (and likely others), using a script with MySQLMonitor seems to leak small amounts of memory. If a script is defined for a monitor e.g. with:
[MySQL Monitor]
type=monitor
module=mysqlmon
servers=LocalMaster1,LocalSlave1,LocalSlave2
user=<...>
passwd=<...>
monitor_interval=5000
script=/home/..../scripts/sql_monitor_script.sh $INITIATOR $EVENT $MASTERLIST

and then MaxScale ran with:
valgrind ./maxscale -d
The output after stopping is:
Shutting down MaxScale

Closed /var/log/maxscale/maxscale1.log
==24105==
==24105== HEAP SUMMARY:
==24105== in use at exit: 187,978 bytes in 3,451 blocks
==24105== total heap usage: 6,583 allocs, 3,132 frees, 2,362,604 bytes allocated
==24105==
==24105== LEAK SUMMARY:
==24105== definitely lost: 1,377 bytes in 9 blocks
==24105== indirectly lost: 0 bytes in 0 blocks
==24105== possibly lost: 336 bytes in 1 blocks
==24105== still reachable: 186,265 bytes in 3,441 blocks
==24105== suppressed: 0 bytes in 0 blocks
==24105== Rerun with --leak-check=full to see details of leaked memory
==24105==
==24105== For counts of detected and suppressed errors, rerun with: -v
==24105== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

With leak-check=full valgrind points towards pcre2_compile_8.