Steps to reproduce:
1. Press twice or Press to Sprint
2. While Sprinting, press and hold
Sprinting FOV is still enabled and Sprint particles still show up under the character while crouching and walking forward.
This bug has been previously reported, but steps for reproducing have not been provided. One similar report is MC-4098. Other reports similar to MC-4098 have been marked as a duplicate. All the reports I've found related to sprinting issues include "sometimes" in their summary or description.