I've gone back to v3.6 as v4.1 is inserting gaps between a flat surface and a wall that sits on it, and also failing to print other walls at all (It doesn't even seem to know they are supposed to be printed!).
I tried several times with v4.1 with exactly the same result each time.
I reinstalled v3.6, regenerated the gcode, and it worked 1st time.
I've had almost no failures since I originally set it up 2 to 3 years ago (I tune and clean it each time it is used), only having failures with v4.1.
I have Win7 Pro x64 (all updates), on an AMD Phenom x6 1055T, 12gb RAM, 500 SSD, NVIDIA GeForce GTX 960 2Gb (8Gb allocated), and a stock Creality CR-10 (with a clean Ikea mirror - no glue).
I only print using the SD card.
I'll wait for the next update to try v4 again.