This concerns a possible filter related bug in version 3.31 on Win7x64 with all patches. The database in use has 361 entries.
I was attempting to use a filter to implement an archive function for obsolete entries. I placed the string :Archive: at the beginning of the Notes field in those entries that I no longer wished to see and created the following filter
1 Yes Notes does not begin with :Archive: (case sensitive)
Initially, the filter appeared to be working as expected and the 20 entries with the :Archive: string at the beginning of the Notes field were not shown. However, I noticed that in the last group (out of ten total), four of its six entries were filtered even though they did not include the :Archive: string. Looking further, I noticed that other groups also had entries filtered incorrectly. At present I do not see an obvious pattern to which entries are filtered out incorrectly.
I've implemented the filter as both session and database and with the database in both R-W and R-O modes. I still have a WinXP laptop lying around and the problem was duplicated there as well.