Mint 18 - Synaptic Package Manager - quick filter errors

[Ross]

1) The version and edition of Linux Mint: Mint 18 Cinnamon 64-bit.
2) Problem: When using quick filter, accurate results are not returned.
3) What happened: When searching for packages known to be in the repositories, the filter results do not show them (see attachment for example). Instead of saying "Quick filter" above the quick filter box, "Rebuilding search index" is displayed instead.
4) Expected result: When searching for packages in the repositories, accurate results should be returned.
5) The problem happens approximately 60% of the times Synaptic is accessed.

The issue does not occur in Mint 17.3

[Martin Dünkelmann (nc-duenkekl3-deactivatedaccount)]

Also, if you remove and then add a new file in
/etc/apt/sources.list.d
while
synaptic is open
it will be frozen.

[Phillip Middleton (pmiddlet72)]

Similar note. However when I test this, SPM takes quite a bit of time hanging in package index rebuild, but then is searchable with the 'Quick Filter' (it's not usable until then). APT doesn't appear affected, so can't say the problem is there.
SPM is version 0.83.
APT is 1.2.12.
apt-xapian-index is 0.47ubuntu8

Note: I have no ppa's attached. This is a fresh install of Mint 18. No previous hassles with SPM in the past. Suspecting this may be a re-emergence of an older xapian indexing issue.