https://gyazo.com/7d7cc400ce5f5ca525ddd82806505119
Only happens when morphed and in third person

As Morph has just been rewritten and released for MC 1.16.5, I am clearing the issue tracker as I have not provided any support Morph for 1.12.2 and earlier. My apologies for not addressing your issue.

Bit late on this one but do you know if there was anything spitting out in the console when this was happening?