In game had 3 kits born to second set of cats, game fine other than the oddity of one kit having sim-specific traits (kleptomaniacfor example). Always used save as and renaming file.

loaded up game today and two are just gone, the remaining kit's family tree ingame has two empty icons unattached to anything. One of the gone kits is/was the one with sim-traits (boy).
The other one however I hadn't noticed anything suspicious on her.

Your family tree is having fall out from them being deleted but unfortunately nothing says what deleted them or why. I suspect they may have had issues internally if they had Sims traits and one of the cleanup mods may have wiped them. From the error Tempest is throwing it looks like you might have an out of date social tuning mod. Have you verified all your other mods are their most recent versions?

Hey there. Mind if I offer a different explanation for the many Tempest errors? Nothing to do with kittens I'm afraid, but as the player does not have Seasons in play the mod is kind of unhappy about not being able to control Trick or Treating (as ToT doesn't exist).

Are we even meant to run Tempest without the EP?

It shouldn't be installed, no. But the error is indicative of the social tuning being missing, which, on a properly patched game, shouldn't be the case whether it's installed or not.

Ah, right. Thanks for the clarification.

Should have Seasons now, so Tempest errors shouldn't be a problem. But the kittens are the interesting problem more at the moment. Ido use MTS's Higher/Lower LTR, Unhidden Traits, AllTraits for All Ages
by mikey.

hmm... kittens oddity...

My xcpt text files do mention such as:

[Exception info]
date: 2017-07-19
time: 13.34.27
type: ACCESS_VIOLATION writing address 0x00000008
address: 0x005a371a "C:\Program Files (x86)\Origin Games\The Sims 3\Game\Bin\TS3.exe":0x0001:0x001a271a

could those help?