I was taught you should never crimp the tips to the cables. You should always solder them together. The crimp causes resistence = heat. My 2 cents

There could be many reasons for your heat build up on the SB connectors. The most prevalent reason that I`ve run across is resistance in the cables due to discoloration due to corrosion. Theres a Billy Joel song that states "you cant go the distance with too much resistance".Check your charger cables and battery cables for wear,Also remember that there is a neglected connector on the truck side that is usally never even considered as heat source. Be sure to crimp or burn your connector tips properly when replacing them.

If you have 1 sb (PLASTIC) connector on 1 charger that has a bent tip or cracked housing, that poor connection on the charger side will cause the connector on the battery side to melt the part of the connector that holds spring pressure (opposite the spring), this in turn will melt the one that connects on the truck, then a new battery in the truck will melt the same section. Take a good look straight down into the connector side and make sure that every SB connector in the place has a good (flat) piece pushing on the tip and it holds good spring pressure. you say they are good, but ANY crack in the housing makes it no longer good, even if it may appear OK all the rest of the way.
You might want to assign one charger to only a couple of batteries for a while to see if this is not a "growing" problem.
You may also want to (should) insure the chargers connectors do not fall on the floor when disconnected, as they can get run over, and look OK externally but have cracked and weakened the part that holds pressure on the spring and contact.
Almost all industrial batteries over a few weeks old will have SOME continuity from the posts to the case. Heck, your body has SOME (that is what a lie detector reads, although they like to refer to it as "galvanic skin response"). You would have to keep the battery top -very- clean and -very- dry not to have SOME. Different controller manufacturers have different allowable maximums, GE controllers say the maximum is 100K ohm, and any less resistance should be dealt with before any sort of troubleshooting should be attempted.
If you ever read the battery manufacturer's instructions that come with a new battery, you may notice they expect a daily charge cycle*, fill with water ONLY -after- the charge, wash off the top and frame with clean (and properly disposed of) water and allowed to air dry. The manufacturer of your car also says (in the owners manual) to check the motor oil every time you add fuel, and I don't know too many folks that do either one. but a good wash and air dry every so often will sure help.
*= a proper charge cycle being 8 hours charge, 8 hours cooling down and 6 to 8 hours operation (we know you don't really drive the lift all 8 hours in an 8 hour work day) with one of every 5 of those cycles to have a 15 or 16 hour charge often referred to as a weekend or equalize charge.

Thanks guys all good ideas. I am cleaning (pm-ing) the batteries. I found contact cleaner in the back , I cleaned the connector contacts. I don't think its the chargers because the charger plugs are fine. Some of the batterys have voltage going through the case...how do you combat that?

If the copper contacts in the plugs are damaged or not clean you would get a poor connection and lots of heat. Did you replace them?

check the charger, may be staying on longer than needed. once any deformation starts the deterioration comes on pretty quick. if the charger connectors are also deformed it started there. if the batteries are too hot to touch with sensitive skin the chargers are over charging or the batteries are defective. i have seen this problem begin when chargers were moved to a 240 source when set up for 208, can also be wrong AH rating you must change all three even if it means cable replacement on the truck side...good hunting.

Have you checked your batteries?
This is a sign of high amp draw, which is creating a lot of heat.
I would start with eth batteries and cables. Clean, inspect, and check the specific gravity in each cell.
If these are all good, then it is time to start with your lifts themselves.