Fundoplication in 1986, having some issues lately, told by specialist my cardiac sphincter is not opening like it should, but not to worry about it ?

Indigestion?: They likely meant esophageal sphincter, not cardiac. I am not sure what issues you are having, if it's indigestion then I recommend modifying your diet to less acidic foods, decreasing the amount of food you consume, adding in some antacids and consuming foods which will move through your intestines faster rather than binding foods such as meats and starches.