This worked for me:
I increased the MAX_TIMESTAMP_LOOKAHEAD in props.conf to 90 . and then I removed the subsecond from your datetime.xml file.
The following is what worked for me.
<datetime>
<!-- Request Set Number: [444888] - Scheduled Run Date: [2020-03-05 16:45:22.0] -->
<define name="custom1" extract="year,month,day,hour,minute,second,">
<text><![CDATA[\[(\d{4})-(\d{2})-(\d{2})\s(\d{2}):(\d{2}):(\d{2})]]></text>
</define>
<!-- [Threat-11] 03/04 17:10:58,109, INFO -->
<define name="custom2" extract="month,day,hour,minute,second,subsecond,">
<text><![CDATA[\s(\d{2})\/(\d{2})\s(\d{2}):(\d{2}):(\d{2}),(\d{3})]]></text>
</define>
<timePatterns>
<use name="custom1"/>
<use name="custom2"/>
</timePatterns>
<datePatterns>
<use name="custom1"/>
<use name="custom2"/>
</datePatterns>
</datetime>
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