[NEEDS SAVES] Upgraded fire-proof objects catching fire a lot

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Often (50% - 99%)
What is your current game version number? n/a
What expansions, game packs, and stuff packs do you have installed? All expansions, Vampires, Outdoor retreat, Spa day, Dine out, 7 stuff packs.
Steps: How can we find the bug ourselves? Have a sim upgrade a fire.
What happens when the bug occurs? Upgraded Fireguarded fires, are catching on fire a lot.
What do you expect to see? Was expecting upgraded fires to not catch on fire, or not more than not upgraded ones.
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. Last patch.

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The fireguard upgrade is causing fires, since the last patch. I had a sim living in VIII Landgraab Apt. After the patch I had a lot of fires including 5 fires in 2 sim days, which is double what I have had since playing Sims 4. I had her move to the penthouse in the Arts district and installed a fire after I had her upgrade it, I sent her to the festival outside. While at the festival I had her light some fireworks and was notified of a fire. I was searching the festival area but could not find a fire, so I checked her apartment and found the fire, it had spread into a second room through the wall, from the bedroom it had started in. My sim lives alone and as the fire had autolight as well as fireguard, I have no idea how it started.

 I do use mods, but have removed my mods folder, repaired the game and started a new game. I moved a sim from my library with the needed skills into VIII Landgraab Apt had her upgrade just 1 of the fires, as soon as I had her walk into the room it caught fire. So it seems very easy to reproduce. The other fire in the apartment that I have not upgraded has not caught fire, even though its been lit since she has lived there.

Edit By Crinrict: Adjusted Title