Looking back through the only thread I’ve played PBF in so far, you can see examples at Casual: Hobusu vs robinz - #84 by Hobusu, Casual: Hobusu vs robinz - #82 by Hobusu, Casual: Hobusu vs robinz - #80 by Hobusu, Casual: Hobusu vs robinz - #62 by Hobusu - and doubtless more if I go further back. You’ll notice that all of these are posts by @Hobusu rather than me, because this error was coming up on preview in virtually every one of my posts - this is why on every one of my posts (or at least nearly every one), there is a blank line between the “in play” section and the “buildings” section, because this appears to fix the problem.
I’ve just looked through other recent PBF threads at random, and found examples at Casual IsotopeX [MonoGreen] vs. Eijolend [MonoRed] - #40 by Eijolend, Casual: Shax(mRed/mGreen/mRed) vs Hobusu (mGreen/mRed/mPurple) - #66 by Hobusu (where it affects “in play” rather that “buildings”), Casual: Shax(mRed/mGreen/mRed) vs Hobusu (mGreen/mRed/mPurple) - #64 by Hobusu and Casual: petE vs zhavier (White mirror) - #39 by petE. From having done this exercise though, it seems that the majority of PBF games are unaffected, so it must only affect some users - although I have no idea why this would be.
I’m surprised that no-one else seems to be able to confirm this - unless they haven’t seen the post yet. I’ve not discussed it with anyone until now, but I assumed from seeing the examples above that this is not a problem that’s isolated to me.