By default Solarwinds doesn't save configs when it logs in to download a config. So that is quite odd. You should make sure you don't have any other triggered jobs that go save a config when it Maybe someone set up something like that in the past, or have only you worked on this server? Places I would look would include the "Device Templates", make sure someone didn't include a "write" command in the login process somewhere. Also, make sure you don't have an alert set up to trigger an NCM job (not even 100% sure that can be done) that logs in and writes out the config.
As far as stopping the downloading loop, you might try setting up your comparison criteria to ignore new configs that have the "last modified by" line changed. Go to "Settings" and "NCM Settings".
In the "Configs" section, go to "Comparison Criteria". Add a new one, give it a title that makes sense to you, and in the "RegEx pattern" put in something that identifies what you want to ignore. ie: if the line starts with "! Last modified by", you might want to put in "^! Last modified by.*". The initial "^" anchors it to the beginning of a line, the ".*" says match anything after that.
By ignoring this line, if no other lines are different in the config it will reject it as being the same as a previous one...
HTH!