Launchd - My periodical task is not executed

Hi, there!

In my the following environment, My task (shell script) is not executed by launchd at the specified time. The task was executed by launchd correctly at least about one month ago.

Model: iMac 27-inch 2017
Processor: Intel Core i5
Memory: 8 GB
Graphics: Radeon Pro 570
OS: macOS Big Sur Version 11.1

As checked system log (/var/log/system.log), I saw the following lines. This means that launchd daemon was killed at almost every second by the SIGKILL message from mds. MDS seems to be related to indexing for Spotlight as searched this forum by using the following result.

Code Block 
Jan 31 21:02:12 iMac syslogd[55]: ASL Sender Statistics
Jan 31 21:03:30 iMac com.apple.xpc.launchd[1] (com.apple.mdworker.shared.09000000-0500-0000-0000-000000000000[5075]): Service exited due to SIGKILL | sent by mds[86]
Jan 31 21:05:03 iMac com.apple.xpc.launchd[1] (com.apple.mdworker.shared.09000000-0600-0000-0000-000000000000[5116]): Service exited due to SIGKILL | sent by mds[86]
Jan 31 21:05:44 iMac com.apple.xpc.launchd[1] (com.apple.mdworker.shared.09000000-0700-0000-0000-000000000000[5133]): Service exited due to SIGKILL | sent by mds[86]
Jan 31 21:06:43 iMac com.apple.xpc.launchd[1] (com.apple.mdworker.shared.09000000-0000-0000-0000-000000000000[5158]): Service exited due to SIGKILL | sent by mds[86]

However, I cannot find any useful workaround or solution for this issue. Can you help me?