The one about the sloped armour reducing the amount of space available internally is a typical Soviet era design fault; immediately postwar, all those "domed" turret designs through the next 10-15 years meant exactly the same thing, a lot of lost/unuseable space in the turret out towards the edges of the curving shell...and on certain models, the autoloader reduced the available space even more!
Regarding the low manufacturing/assembly quality, the hardness of the armour plate, the quality of the welding etc....while chasing down details on the Matilda years ago, I came across a reference to and many pics of the terrible shot traps that bad cutting of plate to size/shape
and welding caused on the T-34
And of course - the hardness of the hull plating, and the time and effort needed to dress down any "proud" edges and joints meant that many were rushed into combat "as is" - with the shot traps unrectified for want of time, labour....and even machine tools!
Regarding the Christie suspension - the Soviets made the best of a bad job; the massed military manouvers of the late 1930s had ALREADY shown up the Christie suspension's limitations...all those newsreel shots of BT5s jumping over walls etc.? Basil Liddell-Hart, as a private press observer by this time, records observing Soviet repair crews straightening out bent and mangled Christie suspension units after each day of the manouvers, in time to appear in front of the cameras the next morning. Simply
scaling up the Christie system for a heavier tank was to send the Soviets down even more of a blind alley...