Hmmm, you seem to be playing as the Chomper correct? If so, there is a bug that could sometimes happen when using goop on someone.
To summerize it all up; people accidentally use their skills while at the same time you "goop" them. This causes a bug where the person that got gooped still have the animation of goop all around their character, but they are able to either move around freely or able to use their abilities at will or both as a matter of fact. Am not sure which skills causes it or what the exact timing to trigger the bug.
Keep in mind that am not 100% sure that using skills at the same time with goop causes the bug, but it's a theory. It happened to me sometimes as well: I get gooped and am able to run freely and use skills.
To enlighten you some more, there's another glitch that the Chomper could do. Sometimes, the chomper swallows the enemy player, but the enemy player just turns invisible then exits your mouth with full health and then becomes visible again (You can tell if this happens if you don't get a vanquish for it). This also causes the enemy player's vision change depending on where he died at. There was one time where this happened to me and bam, turned into 1st person Plants vs Zombies Garden Warfare (It will change back to regular 3rd person vision after you die or leave the match). xD