In some situations, regions that you haven't explicitly set to "Follow Tempo" will have this feature enabled. In other cases, regions that had been previously enabled to Follow Tempo are no longer enabled.
Although the Follow Tempo parameter for elastic audio can be enabled and disabled in the Region Parameter box, it's actually a property of the audio file. This means that if you enable Follow Tempo for a region, all other regions derived from the same audio file will also have Follow Tempo enabled. Likewise, if you disable Follow Tempo for a region, all other regions derived from the same audio file will have Follow Tempo disabled.
If you want to have independent control over the Follow Tempo parameter for different regions derived from a single audio file, there are a few methods. You can select the regions that you don't want to follow the tempo, and then choose Audio > Convert Regions to New Audio Files from the Arrange window's local menu. The regions will be converted into normal, independent audio files that will not follow the tempo if you change it. This method works best if the song is still in the same tempo that the audio file was originally recorded at; converted audio files will always play at the original recorded tempo.
If you've changed the tempo of the song and wish to "lock" some regions to the new tempo, use the Export Region function instead. Select a region that you want to follow the tempo, and choose File > Export > Region as Audio File. Be sure to select the "Add resulting files to Audio Window" checkbox so that the exported region is added to your song. Then drag the region from the Audio window into the Arrange window in place of the original. This file will now play at the tempo that the song was set to at the time of export, rather than the tempo at which the region was originally recorded.