Have you checked that your script produce UTF-8 ?
If not, you probably need to specify the charset associated to the sourcetype used in your monitor stanza so that splunk can convert the text to UTF-8
(so in inputs.conf , you monitor your file and used sourcetype1 (as a example) , in props.conf, you specify CHARSET for this sourcetype1 used.)
The "-too_small" suffix is added by Splunk when it doesn't have enough data to guess about the correct sourcetype. The fix for that is to provide a sourcetype in inputs.conf so Splunk doesn't have to guess. This a Splunk Best Practice.
If you provide some sample data we may be able to help with the necessary props.conf settings for the sourcetype.
--- If this reply helps you, an upvote would be appreciated.