Tuomas,
I apologize for being so late responding. I am almost certain the loss of formatting occurred with the upgrade of my phone and tablet from Android 9 to 10. I dug up an old, discarded phone which was on Android 6 which I haven't used for many months and installed the hisb.zip and the CSS files. It formatted correctly. I then updated ANDBible and the formatting held, so it is not recent changes to ANDBible that caused the issue. Unfortunately I can't upgrade the Android version on that phone, but I think that what I have done pretty well points to the change from Android 9 to 10 that is causing the problem.
Thanks for your willingness to look at this,
Ivan Hipschman