Recent used files not on the list or on top of the list while searching for it

Hi there!
For years I have enjoyed this app, thanks a lot for your work on it! But since a few weeks, probably since upgrading to Ubuntu 18.04 (Gnome) most of the recently used files would not show while searching for it. There would not even be a suggestion, so I have to press "enter" to start a search to get any results. The search result list is not (as before) ordered with the most recent used ones on the top. I use Synapse 0.2.99.4-1 on Ubuntu 18.04 (Bionic Beaver).

I had a similar problem in 2011 (https://answers.launchpad.net/synapse-project/+question/161068) and deleting the zeitgeist-files (see below) helped but this time not.
zeitgeist-daemon --quit
cd ~/.local/share/zeitgeist/
rm -rvf fts.index/
zeitgeist-daemon

And I also delete the sqlite-files which are rebuilt afterwards.

This is what I get run synapse from the terminal, synapse had a crash after the first start:
$ synapse
[INFO 11:22:06.550922] [synapse-main:267] Starting up...
[INFO 11:22:06.736094] [synapse-main:209] Binding activation to <Control>space
[INFO 11:22:06.763957] [view-base:251] Screen is composited.
[INFO 11:22:06.764159] [controller:56] Using ibus input method.
[WARN 11:22:06.926675] [GLib-GObject] cannot register existing fundamental type 'SynapseUtilsAsyncOnce' (as 'ZeitgeistSymbolInfo')
[FATAL 11:22:06.928494] [GLib] g_once_init_leave: assertion 'result != 0' failed
[WARN 11:22:06.928525] [GLib-GObject] cannot create new instance of invalid (non-instantiatable) type '<invalid>'
Trace/breakpoint trap (core dumped)
$ synapse
[INFO 11:23:35.451944] [synapse-main:267] Starting up...
[INFO 11:23:35.540009] [synapse-main:209] Binding activation to <Control>space
[INFO 11:23:35.569484] [view-base:251] Screen is composited.
[INFO 11:23:35.569709] [controller:56] Using ibus input method.
[WARN 11:23:35.884073] [desktop-file-service:76] X-Cinnamon is not understood
[WARN 11:23:35.913284] [desktop-file-service:200] Unable to get exec for GNOME Shell integration
[WARN 11:23:36.094472] [desktop-file-service:200] Unable to create AppInfo for /usr/share/applications/openjdk-11-policytool.desktop
[WARN 11:23:36.186281] [desktop-file-service:200] Unable to create AppInfo for /usr/share/applications/vim.desktop
[INFO 11:23:36.610033] [gnome-session-plugin:158] org.gnome.SessionManager is available
[INFO 11:23:36.987012] [hybrid-search-plugin:179] keeps in cache now 509 file names

It seems that somehow Zeitgeist is not working although I enabled the plug-in zeitgeist and hybrid search.
Do you I need to install the xapian-tools?
Any tips?

Thanks!