This is a genuine Minecraft gameplay-ish bug even though I mention the launcher in the beginning. When changing the version you are playing with in the Minecraft Launcher (without any new keybinds besides mods) the controls you have equipped will reset to all defaults (including mods). Please change this bug as it is really annoying to go from playing on laggy servers like the Hypixel Network to my own 1.13 server, switching versions to do it, then going through the process of redoing all my custom controls again. Here is an example below. Thanks Mojang!

My movement controls in 1.12.2 (OptiFine) are:
Jump: Space (default)
Sneak: Left Control
Sprint: Shift
Forward: Up Arrow
Backwards: Down Arrow
Walk Left: Left Arrow
Walk Right: Right Arrow

My movement controls when upgrading to 1.13 are:
Jump: Space (default)
Sneak: Shift (default)
Sprint: Left Control (default)
Forward: W (default)
Backwards: S (default)
Walk Left: A (default)
Walk Right: D (default)