50mm lens recommendation

I have a 6D (full frame) camera. 50mm is the focal length I use the most (also have 20mm and 85mm). I do not use autofocus.

I have a 50mm 1.4 EF lens. I like the image quality, and low weight and compactness. However the focus often becomes stuck, requiring dissassembly and bending this part back into shape. I could get the same lens again. Are newer models less prone to this particular focus issue?

I have also seen the 50mm f/1.8 STM lens recommended. Is this really as good as the old 1.4 despite the low price? I could survive with only f/1.8 as long as it is very usable wide open.

I didn't find the right solution from the internet.
References: 

https://www.dpreview.com/forums/post/60337095

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