Why are apps excluded from Titanium Backup?

I have been using CM Browser for couple of years. A couple of months ago I set Titanium Backup ( Pro - version 7.5.0) to backup on schedule as shown below ( 3 as maximum backup versions ):

After the last update of CM Browser, which I didn't like, I uninstalled it, being sure I could switch to the earlier version. Surprisingly, I didn't find CM Browser backup !

To doubly verify, I installed CM again and took a manual backup (by force-running the schedule) and sure enough it didn't show up – despite of the "backup completed" toast being shown (no error message in between either). And yes, I've verified that I didn't have any filters set that might be hiding it.

It can't be a version issue of Titanium as the previous version should have retained 3 backups.

Why is this so? What makes apps "unbackable" ? How do I fix this?

Device: Moto X Play, 6.0.1, stock, rooted

Edit:

1. 
   

   As suggested by Izzy in comments, searched the backup directory and found backups of Browser. Installing the apk from there got me my old Browser version but minus the bookmarks ( Data for apkalways included in preferences).Backup of newer version also present in apk

   
   
   


2. 
   

   Mailed the developer. Will post updates but meanwhile ideas to troubleshoot are welcome

   
   

Edit 2: when I took a logcat for the second time (in the process of installing app and forcing a backup), TiBu mysteriously decided to show me CM Browser with all previous versions and data intact. I haven't the faintest idea and will post an answer if the developer clarifies. I have mailed him the logcat. Pastebin here

You are welcome to post your answers