The bug
The part of a valid tripwire setup which is within the hook's block space will have stretched-out pixels, compared to the rest of the tripwire. This results in these pixels looking rectangular rather than square.
How to reproduce
Create a tripwire setup by placing string between two hooks
Pay close attention to where the tripwire meets the hook
Expected results
All pixels of the tripwire would be square.
Actual results
Those closest to the hook are rectangular rather than square.
Relates to MC-13485.
Confirmed.