Heya friends, thanks for the report and sorry for the death! We just tracked this bug down and have a fix in for upcoming patch 1.02.
When you lift up the orb channeling key at the exact moment that you finish picking it up, the bug could cause the server to get stuck thinking that you were still holding the key down (more likely in poor networking conditions). When that happens, the next time you come across an interactable (another orb, planting the bomb, etc), you'd automatically start using it. We've only seen the auto-plant issue impact players who map their Use Orb and Use Spike buttons to the same key, causing both to get stuck down when this occurs.
Until that patch drops, the easiest way to prevent this from happening is to either tap the interact key again after picking up an orb (to guarantee that the client and server get back in sync), or to hold the key a moment longer after finishing the orb grab. Alternatively, if you split these keybinds to diff...
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