I'm guessing that you are using search time field extraction.
If you are using search head clustering behind a router, one search head has the correct props.conf and another does not.
Any time the sourcetype is modified, you must cycle Splunk. First try diff'ing props.conf and/or transforms.conf between the two servers. If they don't match, that's your issue. If they do match, cycle Splunk on the server that's not parsing properly.
Also, for search time field extraction, props.conf must exist under the context of the search app. On the server where the results are different/unexpected, ensure that the correct sourcetype exists, and is in the correct context (.../etc/apps/search/...) eg.