I know this is an old thread but I had this issue this evening and wanted to contribute what I had to do to fix it.
I had replaced the 22_On_time.ogg file with my own and the proper case sensitivity was adhered to, however, it would still play a random mp3 from the internal SD storage. I tried replacing it with the original and it didn't work (before I realized that a reboot was necessary, so that may be why it didn't work) and fought with it for a couple of hours this evening. In the end, it was fixed after I did the following things:
1) I opened the original OGG in a sound editing app named GoldWave, the audio config for the original was Vorbis, 44100KHz, 128Kbps. For some reason, GoldWave wouldn't let me save my OGG file to this configuration, closest I had was 120Kbps. I copied my audio, pasted it over the original audio and then did a Save-As and GoldWave allowed me to save the "original" to the original's native 128Kbps.
2) When I moved it to the /system/media/audio/notifications location, I first deleted the 22_On_time.ogg file that I'd placed in there from previous attempts so that there was no file whatsoever; rebooted the phone, then moved the ogg file to the proper location, rebooted again and it worked fine after that.
I have no idea what the actual fix was but just wanted to share my findings. Those were the last 2 steps I did before it worked so I'm attributing my success to one of those steps.
Additionally, the weirdest thing I observed was, prior to the steps that ultimately resolved the issue, if I had the phone hooked up via USB, debugging mode w/the SD cards mounted, it played the custom 22_On_time.ogg file. If any of those things was different it would keep playing the mp3 from my internal SD card. I have no idea why.
Hope this helps someone at some point down the road.