Hello
Bearings on differential: on post #27, I explain there is a problem with the first batch of E4RS II EVO (problem solved on second and other batches). To quick fix this little problem, you could simply use sand paper: cut a stripe on a sheet of #400 or #600 sandpaper, and place it around the ball bearing location on the diff case... and simply turn the case with the other hand for a few seconds. When your bearings would be correctly placed, free in movements, you will probably no more have the problem of bearing housing "vibration" (I think your orange inserts are moving a bit laterally because bearings aren't well aligned).
CVD blades: it's true, the blades are hard to insert, because we choose a very hard material for longevity. To insert the blades, I start to introduce one side of the pin on one hole of the blade. I use a lighter to warm the central part of the blade. Right after, I use a long nose plier to place the blade over the second pin. When blade is in place, there is too much play... to "close" the blade around the driveshaft ball, I re-use the lighter to warm a bit the central part of the blade and I maintain the blade on the ball while it cools.
E-clip on piston: yes, on the first batch the room for the piston was a bit too small (this as been corrected). You could use light sandpaper to give more space to the E-clip.
Screws on hard plastics: for the first assembly, you can put a bit of grease on your screws, this will help them to create the thread on the palstic.
Pivot balls: No problem with the lenght if you use 2mm spacer. It may looks too short, but we have for sure no problem with 2mm spacer, don't be afraid about it (we also used 2.5mm without problem). For more spacers, you have to use Team Magic 503138 7mm pivot balls. Why don't we provide the 7mm pivot balls in the kit ? Because with less spacers (2mm and less), the pivot ball could touch the diff outdrives... and this is really not a good option
Short pivot balls would be ok in 80% of the cases.
Rear anti-roll bar ball cups: yes, this part is new and we don't had real feedback on it before releasing the kit. We will ask TM to modify a bit the mold, to provide a bit more plastic around the screws. Be care to don't overtight them.
I hope I answered all your issues - sorry for my "Swiss made English"