Same issue. Is there a bug opened for this ?
On my phone, I also have the option to choose voice typing rather than hitting the microphone button on the keyboard. If I do that under a bullet point or heading, it immediately closes. I have no issues in other apps.
Given the timing of this showing up, I may downgrade my obsidian version to 1.5.8 . A user mentioned doing that in this post Cursor ends up before the letter on android Samsung keyboard - #41 by jakpri . Even though that issue is different than this one, there were a lot of keyboard related changes made in 1.5.9 . Currently none of the major android keyboards are fully functional. Samsung, gboard, and swiftkey. If it is possible, all of these keyboard related changes should be rolled back until a fix can be made.