do i have transmission problems or sensor needs to be replaced? on 2001 Hyundai XG300

my car have hard time shifting out to 3rd occassionally,so i had trnsmission flushed and refilled.That didnt fix my problem,i can drive it for @3 days and it drives fine then it will do it again not shifting and if i keep pressing gas the rpm hand rises up to about 4 and jerks into gear.

Asked by for the 2001 Hyundai XG300