The bug

Right-clicking (or pressing your 'Use Item/Place Block' keybind if different) on a sign that isn't glowing, while holding an 'Ink Sac' doesn't run the clickEvent, but still plays the hand animation. Same works with a 'Glow Ink Sac' on a glowing sign

How to reproduce

1. Run this command:

   /give @p minecraft:oak_sign{BlockEntityTag:{Text1:'{"text":"[CLICK]","clickEvent":{"action":"run_command","value":"say Test"}}'}}
   

1. Place the sign you've just been given
2. Right-click (or press you're 'Use Item/Place Block' keybind, if different) on the sign
   → You should see "[yourUsername] Test" pop up in the chat and a hand animation play
3. Repeat step 3 while holding an 'Ink Sac'
   →  You should see the hand animation play but nothing will appear in chat