From past experience it can be any mod's srs which is causing the issue, not simply the two in question.
My most used installation has only 8 series, and only 1 stock series. I had to mess about to get them showing properly. In the end, it was easiest to remove Order=# from all my mods (but not the stock reiza## series) and just let the game order them alphabetically using the name of the srs file. It will always try to put reiza## series first, and then the mods line up alphabetically after.