I couldn't find a similar thread for this. (Except for ones that generalized buggy players in the beta.)
Let me give you an overview of my fm save first before I explain. First season with Toulouse, I came 2nd. Second season, third and in the champs league final (wtf!). Third season (this current one), after improving my squad massively, but only making one change to the first team (upfront, so the defensive chemistry was unaffected), I was 8th in November. My defence leaks in goals constantly. In fact more than ever, despite the players' stats improving all the time.
After tweaking the tactic enough, I've realised that it's only player mistakes costing me. So I brought in a top GK on a free, and since then have gone 11 unbeaten (IMO thanks to his better communication, commanding the defence). However, on this good run, the only players under an average rating of 7.00 is my fullbacks, Serge Aurier and Cheikh M'Bengue (the latter having very solid stats). Now I know they're no world beaters, but going on the teams in Ligue 1, they are more than good enough to handle half the wide players in the league. There's FBs at AS Saint-Etienne and Lille, who are not as good as mine, getting better ratings. And in the course of 2 and a half seasons, I've tried different settings, whilst still giving them time to adapt - with no success.
It's starting to become frustrating that no matter how well I do, what teamtalks I give, what OI's I set, the fullbacks (or a mistake from my CB's due to not concentrating) will gift a goal. In my 11 unbeaten games, I've only kept 1 clean sheet.. and I'm pretty sure that was a 0-0.
TL;DR: I'm sure I've waffled a bit, but basically they must be bugged? Players acted like retards in the beta, but overall they seem ok now, except the fullbacks. It seems that unless I have world class ones such as Alaba on each side, then I'm doomed to concede from wingplay.
Here's a screen of my current fullback settings. I'd appreciate it if you could either share your similar experiences (confirming that maybe the fullbacks need fixing), or a proven setting that has the FB's performing well.
P.S. I don't believe the wingers being so high up to be a problem, as their mentality is set much lower than it would appear, and the FB's mostly get beaten 1v1 anyway.
On second thoughts maybe this should be in the tactics section. I'll leave that to the mods to decide. Cheers!
EDIT: I might try lowering their mentality massively and having their 'runs from deep' set to never. I'll update how that goes.