Am I the only one that doesn't actually think tonight was part of some wider issue, or proof that they're 'bottlers', but just one of those freak results that happen now and again?
Yes and no. The wider issue wasn't the comeback itself (ie. the "bottling"), but the fact that Anderlecht over two (!) games was able to match Arsenal... without some bottling of their own Anderlecht would've won the 1st match, and they created chances throughout the entire game last night (as early as the 3rd minute and as late as the 90th). For years now Arsenal attempt to play positive combination football inside the opp. half without having either the personnel or (far more crucially) the mindset to deal with DF transitions. That is on Wenger. Look at Real Madrid, their starting XI this season has no specialist holding mid or "destroyer" either (MF comprised of Modric, Kroos, James, Isco, basically four playmakers), yet it works because Ancelotti got James and Isco to run and work for the team (though we are yet to see how well their DF coordination holds up against a Bayern, Dortmund or Chelsea for example, but at the moment it's functional enough for the vast majority of their games, something which can't be said for Arsenal).
Forget pundits last night calling them tactically naive because they weren't sitting back on their lead (which is, frankly, bs), the issue is that Arsenal don't know how to defend transitions: firstly there is no collective pressing scheme whatsoever, just individuals chasing balls or standing off, and secondly there is no systemic urge from players ahead of the ball to run back and help out when they've been bypassed. A little pragmatism could go a long way, but so much about Wenger breathes an air of nonchalance when it comes to dealing with opponents (despite, ironically, being well informed on them). It's not even that he actively underestimates them or anything, rather that he seems to overrate his own players' ability. Didn't he also once say the best players don't need to be coached, just to let them do their thing? If ever anyone embodied that clichéd phrase oft-employed by weary managers in the press room which is equally a modern football player mantra ("we just focus on ourselves, not the opponents bla bla"), it's him. That might've worked when at least his team balance was right (ie. a MF anchored by a Vieira, a Pétit) and the context too (tactically fairly simplistic landscape of late 90s/early 00s PL).
All that doesn't take away from Wenger's overall achievements, just saying everyone has blind spots...