While servicing my X1C today I found something very interesting that could contribute to printing issues
It is well documented that a lot of the build platforms have deviations in them but this may help with slight imperfections in the flatness
I found while cleaning my lead screws and guide rods that the brass lead screw nuts have some slop in them
No big deal except that my front left lead screw had no play and seemed to be sort of jammed in the downward position (I could not get the movement upwards like the front right and rear)
Some slop movement between the lead screw threads and the brass nut inner threads is to be expected, not much but more than you would think
In my hurry to service my printer and start another print after finishing a large one with my bed at the bottom in my haste I hit home and well…we know that sound when it bottoms out 
After cleaning the rods and screws with just a slight bit more pressure upwards than the other 2 lead screws a little pop and now all 3 have the same amount of play in them
This is not a large amount, but enough that if one of the screws is not in conjunction with the other 2 I can see how it would cause layer issues
Check out the pictures and its worth checking your printer especially if you are having issues getting proper layer adhesion or artifacts that are more prominent to one corner of the axis
