DIAGNOSIS A steady, gentle hiss from the steam release valve is normal. Hissing/spurting from the *sides* of the lid means it's not sealed. The sealing ring is probably dirty, damaged, or misaligned.
FIX Turn the cooker off and do a quick release if safe. Let it cool. Remove the lid and take out the silicone sealing ring. Wash it thoroughly in warm soapy water, checking for any nicks, tears, or bits of food debris stuck in the groove. Dry it and reseat it perfectly.
IF THAT DIDN'T WORK Inspect the lid itself, especially the metal rim that contacts the ring. Look for any warping or debris. Also, ensure the steam release valve is fully seated in its position (not loose).
HEADS UP Silicone rings absorb odors and need replacing about once a year, especially if you're getting poor seals. A degraded ring is a common culprit for steam leaks.