FAAF

More test results... The speed debuff related to attacking a bug is related to disabling "the quickness". Summary so far... If you don't have an item or status that includes that buff, then you don't notice the change. Once you attack an insect, "the quickness" appears to be disabled. It's not until you defeat an "angry" type bug that it turns off. If you've attacked a "neutral" or "harmless" bug but failed to kill them you have to despawn the damaged bug (leave the biome for example). If you've killed the neutral or harmless bug, you have to trigger a new angry bug to re-enable the quickness (without attacking the angry bug, otherwise you've started the whole process over again and have to kill the angry bug). My results are observation based, so they may be somewhat inaccurate.

It doesn't always go away with sleep. I've had it go away when I defeat the bug that is agro on me, but that seems to be the case only with aggressive bugs. Neutral bugs, if you don't kill it (like the scarab getting shot once and then escaping) the debuff doesn't seem to go away until something triggers the bug to despawn (like leaving the biome?). I killed a weevil and the debuff didn't go away when it died and the debuff didn't go away with sleep. I tried going to the oak tree to break the debuff, but it only seemed to turn off when a wolf spider became aggro'd on me. The debuff ceased at that point and I ran back to my base. Since this movement speed debuff makes fighting impractical, I'm going to be studying this glitch until it gets patched. Not much else I can do...

Confirmed. I too have this problem. I first noticed when killing a grub, my movement speed was drastically reduced after killing it. It's a hidden debuff that goes away after a time. It can also go away with sleep. I shot a glint beetle with a crossbow and had the same issue. It also happens when I fight termites. It did NOT happen when I fought and killed a red worker ant near my base.