You can’t move backwards while jumping and sneaking at the same time.
Reproduce:
hold spacebar and shift
hold s
notice that you don’t move backwards when you should
Related issues
Comments


No it’s not a keyboard issue I can walk forward while jumping and sneaking
Depending on your keyboard, some specific key combinations don't work.
I'm not able to reproduce your issue.
What keyboard do you use? Does the issue also happen when using a different keyboard?

Strange it doesn’t happen on my other keyboard. How do I fix it?
Use the other keyboard.
This is a hardware issue, not an issue with Minecraft. See MC-54194
This might be a keyboard issue. I have noticed before on my laptop that it can only handle 2 different keys at once in some cases.