According to https://www.ibm.com/support/pages/apar/IJ44131, since 7.5.0 UP3:

Systemd can write failure status messages to the logs for the
accumulator_rollup service when the accumulator is functioning
as expected.

As the accumulator_rollup.service will stop when a rollup is
complete, the following systemd message is considered benign:

systemd[1]: accumulator_rollup.service failed.

If the vendor tells us that such behaviour is expected why they can't simply add
....
[Service]
SuccessExitStatus=143
... 
to accumulator_rollup.service?

After the update package 3 I hoped that such systemd reaction on expected 143 return code will be fixed by vendor, but nothing was done even in UP4 and UP5.