There's some bizarre behaviour if Yoshi rolls and holds shield before the roll ends and lets go shortly after, it makes Yoshi stay in shield for like 36 frames during which you can only do OOS stuff like jump/roll/spotdodge even if you aren't holding the trigger down (Yoshi's rolls are 34 and 37 frames long too so this may be a bug related to it). Again this is just a regular shield, and it keeps getting darker/closer to shieldbreak during this. This is exclusive to Yoshi and didn't exist in Brawl or Melee so it's definitely a bug!
To reproduce this as Yoshi, do any roll and hold shield during the roll. Shortly after the roll ends (so Yoshi is now in shield), let go of shield.
To reproduce this as Yoshi, do any roll and hold shield during the roll. Shortly after the roll ends (so Yoshi is now in shield), let go of shield.