This seems random, and could be an issue with two conflicting torque systems, but when two vessels dock together and a Kerbal EVAs to use the KAS connectable struts to strengthen the connection, sometimes on the second or third connection the craft violently rips apart. Sometimes it merely rips the connector off which jumps into 'ridiculous speed', but more likely the whole area at docking port is sheered off.

It seems random in effect and I've successfully reloaded and recreated the problem, but also managed (after multiple attempts) to finally connect four struts by saving and loading before connecting each one. At other times the strut connection on the same craft has had no issues at all. Docking orientation and the resultant angle of the struts seems not to affect whether this happens or not.

This is still happening in KSP 1.2.2 / KAS 0.6.2 , and I have a quicksave that can reproduce it fairly reliable (3 out of 3 tries, for me). I'll make a copy in case anyone wants to look at it. With this quicksave, there are two ways of blowing everything up:

• Burn (hard sudden burn is fine), timewarp, return to normal: Core module of drill rig shakes apart and parts go flying.
• Weld the docking ports: Vessels turn off physics, ports disappear, vessels instantly close the distance between them and connect, and then turn physics back on. Struts reconnect successfully, but then the core module of the drill rig explodes and parts go flying. They fly away from the overall CoM in a fairly spherical spread, they are not flung to aft by the weld warp.

Vessel details

• Two vessels ("Master Blaster" skycrane and drill rig) joined after separate orbital constructions, with Ubio Construction docking ports.
• Mass: 185,000 Kg. The drill rig is very dense.
• 4 EVA struts supporting weak docking port joint, connected to main structural / load bearing module of each vessel.

Here is the overall vessel, with the Kerbal Engineering info. I just realized that it is extremely OP for Mun.

Here is a closeup of the four EVA struts that bridge across the docking connection, showing what they are connected to. The EVA strut is part-highlighted.

Observations

• The vessels are rock solid under max acceleration, and do not require throttle easing.
• Explosions are often preceded by crazy vibrations that rapidly increase in amplitude. What drives this? Where does the physics engine get the kinetic energy from? Where is the potential energy stored? Not in an elastic collision, these two vessels were built separately, and are unable to clip through each other during docking.
• I have seen this type of failure (extreme vibration increasing to destruction) once before, when I tested a very heavy vessel on a weak landing module. For some reason, instead of just crushing the landing module, a more centralized, but still largely load bearing, module vibrated the craft apart. That vessel did not use EVA struts.
• Suspending 200 tons by four struts, in a ~1G acceleration + engine vibration, might be unreasonable. In that case it would make sense for the four struts together to destroy the part that they are holding. However, this shouldn't happen while free floating after time warp. When there is no energy being put into the craft (e.g. burning engine thrust), existing vibrations should not amplify (not the fault of this mod, I am sure).

More Data

I can't post a zipped save file here, but I've kept a copy in case anyone asks for it.

Compensating Measures

• Removing the stock struts from the area between the endpoints of the KAS struts, that is to say, the struts from the parts between the primary structural components of each vessel, eliminates the crazy vibration, and greatly reduces spontaneous disassembly.

I've had similar luck, though my first ever EVA strut caused an explosion. I've had a few go well since, and then another explosion. Not that I expect that this adds any really valuable information other than, it's not just the OP.

I'm happy to contribute saves or whatever else might be useful.

Thank you!

It looks like a physics behavior which has changed dramatically in KSP 1.1. I close this issue for now. Feel free to reopen it if you get the same behavior in 1.1 as well.

I had the same experience last night when linking two pipe connectors together. The source port was on one craft attached near the base to a fuel tank (the source port originated, however, from the target craft and was moved in EVA to the source craft). The target port was pre-added to the target craft in VAB. Both ports were facing each other, not exact, but close. When the link was pulled from the source craft to the target craft, upon linking to the target craft, the source craft ripped into hundreds of pieces (not all parts detached, but most did) and flew apart at ludicrous speed, with the bulk of the large parts landing near each other 13km away on the Mun.