Cutting off the strings attached to tripwire hooks will still emit a redstone power. Cutting it with shears, however, doesn't trigger the tripwire hooks to emit a redstone power.

This bug just changes the block state of the string to attached: false then goes back to attached: true when cut with shears. Cutting it off with shears two times before block state changes to attache: true somehow works.

When you cut the strings with shears and you experienced the bug then tried to cut it off with bare hands, the bug will still happen. The other strings are not affected. Even if you cut off the other string with bare hands, reattached it then tried to destroy the string you cutted off earlier with shears, it will still hold the bug. If you destroy a string with bare hands unaffected by the bug but didn't reattached it and destroyed the string affected by the bug, the affected string will drop, however.

Also after cutting off the strings with shears, the targeted block will be the one on the ground in less than a second then the targeted block will be the string you tried to cut off, again.