Nether portal shield bug

When i been teleporting to nether once i been holding the shield and when i appeared, i cannot get damage, when i got attacked, the shield still been blocking damage, however i can still attack, when i hold shield again the bug dissapeared.

 

(I can't send the video with the bug because of it size, so i give here link to youtube)

 

https://youtu.be/HITIfJGqWuA