As of recently, the game has started wiping my custom mechs and Lances for Skirmish mode. It happened when I started a new Career playthrough and shortly after when I started a Flashpoint campaign. I am not sure if that is related, but each time the save files of the game change in one way or another, the game "eats" most of my Skirmish mode Battlemechs. It always reverts to the same point too.

Since mods were causing problems in the game, I have disabled them from the game's configuration menu. But this disappearing of custom mechs is starting to be annoying. What could be causing it?