OK. first off, please turn off your caps lock button.  You're "shouting" and some consider it rude.

Assuming you're using USGI mags, and the mags aren't buggered up, then yes, maybe the mag catch,  and/or its spring are faulty.  If you aren't trying to restore this carbine to "as-issued" condition, you ought to use the later style of mag-catch which was specifically designed to be used with 30-rd mags as well as the original 15-rd mags ( this is often referred to as the "M2" mag catch).  Original 15-rd mag catches do not work well with 30-rd mags.  Go to www.fulton-armory.com and they will have the parts you need.  I strongly suggest you get Scott Duff's M1 Carbine Owner's Guide which is also available from Fulton.