zf_warhead seems to have a broken door that locks the survivors in the spawning area without any health or ammo kits.
zf_isaac is unwinnable for survivors if they pick up the Polaroid either intentionally or by accident.
zf_logfort has an exploit where zombies can leave hunter marks on unreachable roofs above survivors, letting them attack survivors immediately with impunity and is generally poorly balanced, lacking in supply kits and cover. I actually went and counted and there are only 3 health and ammo kits, all of which are small and very spread out.
zf_harbor is a poorly balanced attack/defense map where the zombies have spawns within 10ft of the first two caps, there is a complete lack of cover in the map, and nearly no health or ammo kits. The control points are all in wide-open spaces without any real cover for them. This basically allows (again) hunters to place spawn markers behind their spawn locations and get in and kill players with impunity. The map also has a distressing lack of pick-ups (a single medium ammo kit and small health kit for A and a small health and ammo kit for B). Overall the result is that survivors have yet to win any rounds in the times I have played it. Not even once.
I may not post here often, but let me give you the lowdown on each.
zf_warhead_mesa's door shouldn't be broken, as far as i've known the map has not ever been updated, and the door works by a survivor standing in the marked area in front, at which point it will slowly open. If there's any problem, my only recommendation is to have the Admin update the map with a different version. Until that happens, should the door be 'jammed' persay, just don't use pyros unless you have supplier and a medic. Otherwise, rely on explosive jumping, sentry wrangling, or other such tactics to skirt the wall.
zf_issac cannot be fixed, the particle effects for the polaroid are simply missing or unusable. The only thing one can do is inform everyone on server of the problem and pray nobody picks it up, it's primary spawn location is in the Depths section of the map behind a breakable wall, usually on a pedestal or floating. The map itself overall is fine, its just that these missing particle effects break the cathedral.
zf_logfort is more of a teamwork driven map. Although I am personally not its largest fan, the problem is remedied by survivors using the lower sections as cover from hunters, and a good team with at least 1 medic of holy-user, and a supplier, makes for a simple victory if one closes themselves in, but not so much as to be affected by sick or tar.
zf_harbor is a map where really the teamwork portion needs to come into play. Don't bullrush over to the first two points unless you know you can put up a good defense. In any case, don't spread yourselves thin, or it'll just be hunters. For the matter, bring along a supplier or two if the ammo becomes a problem. Basic ZF survival rules also apply, but if you find yourselves unable to win. Attempt to hold the last control point instead. It's easily defendable even if no one stands on it due to the open ended nature of it. I've beaten the map plenty of times myself as both sides, and most of the time the RED team wins by a good dose of Teamwork. Sadly, that seems to be lacking these days in alot of teams.