Some fields with >90% coverage disappear randomly between searches

[funghorn]

So this is a prerequisite-free kind of question about a field disappearing from "All Fields" section. By prerequisite-free I mean that search time frame, number of events found, search string and search mode are stable/same and all events have a single sourcetype.

Say I have a field called "info.event_type" that has coverage of 100% (all of the conditions from the first paragraph stay the same throughout all steps). This is what is happening:
1. I do a search and see the field in "All Fields" and "Interesting Fields". I can select it or it can already be selected by me previously, this does not matter (it seems).
2. I repeat the exact same search by clicking the search button and the field disappears from everywhere - selected, interesting and all fields, it's not searchable in the filter box of all fields window.
3. I repeat the search again, maybe a couple of times in a row, field does not appear.
4. On one of the retries it appears and is present everywhere, as before.
5. Next search request makes it disappear again and the circle continues...

What could be the reason for this behavior? Do you know where I can look in order to check for inconsistencies in configuration, etc?
Thanks!

[PavelP]

Hello @funghorn ,

can you repeat your search using other time frame, like "last 24 hours" and use "verbose mode"? Any hints in the search.log?

[funghorn]

Same thing. I've tried looking into search.log files of a search that succeeds in extracting "info.event_type" at search time and a search that does not - there is no mentioning of anything like "event_type" in either file, particularly I was expecting to see it in this line:

05-05-2020 12:10:09.484 INFO  LocalCollector - Final required fields list = *,Message,_bkt,_cd,_raw,_si,_subsecond,action,bytes_in,bytes_out,category,clamav_action,crit,dest_host,duration,eventtype,host,http_user_agent,id,index,linecount,main_sig_ver,message,message_extended,msg,null,ossec_group,ossec_group_list,process,product_version,request_content_type,rule_number,severity,signature,signature_version,source,sourcetype,splunk_server,src_ip,status,type,uid,vendor_product,vendor_severity

The only place the field name is mentioned is in the results in buckets/ and /events dirs.
I've also thought that the following line is relevant to my problem, but it's just a coincidence between Splunk eventtypes and "info.event_type" field, I guess:

05-05-2020 12:10:09.574 WARN  FastTyper - Eventtypes may be incomplete. Event length=152930 is more than maxlen=10000. Please consider increasing the maxlen value under [typer] stanza in limits.conf