My ver 3 MC3000 (2017 production with 2 fans) sliders were very hard to slide. SkyRC stopped using grease and definitely have stronger springs installed. I could hear and feel rough metal to metal contact due to the fact they do not take the time to debur and or polish the surfaces. Other users have also complained about this and have reported the sliders actually bending if pushing back on the top of them. Mine never bent because I only pushed on the bottom but then your finger is in the way of the battery. This can be solved by taking the unit apart and polishing which I was not about to do!
So I ordered a 1.6 ml bottle of DeoxIT Gold with a built in applicator brush for $8.80 from Amazon. This liquid has some cleaning properties and prevents oxidation of contact surfaces without introducing electrical resistance. Contacting the mfg I found it is made with a mineral oil base so it is also a lubricant. The very small brush is perfect for applying it to the sliders and rails with out taking it apart.
10 min later I now have rails that I can push on the top with out worrying about bending and slide almost as easy as the ver 2 with the lighter springs. My IR measurements are now more consistent as well.
1.6 ml is enough to lube a hundred chargers and can be used on all contact surfaces such as ear phone jacks, USB jacks etc etc that you want to give a better connection. It is safe on plastics and it works on all metals (not just gold). FYI it has a shelf life of 5 years or more but the bottle must be kept out of the sun as UV causes the chemical to deteriorate. Sure fixed my mp3 players head phone jack static. Great product!
Going to give it a try on my MC3000 with two fans as well as the sliders are almost binding now. Going to try it first on my first mc3000 as it has one bay that has failed, just in case the mineral oil seeps down and goes where it shouldn't and possibly cause problems later on.