The "round disc" is usually just secured by a thread tied around its "neck". You can snip the thread - carefully- and then move the round disc up a bit, then put another thread around it and tie it off. Since the tube and round disc is a one size fits all, many doctors leave either too little or too much room in placing the round disc bumper or at least that was my experience over the last three years of getting the tubes in.
Or have the doctors do it over - right this time-. The measurements should be when the patient is lying flat and then again when sitting up, and adding them and dividing in two.

Also there is a whole internet forum on putting real food down a feeding tube - if you are interested, I'll post the link - My wife is more comfortable with me doing Jevity for breakfast and lunch but we do our dinner of the exact same food together with the Vitamix.

Sorry you have to deal with this.
Charm