SMPS' improper lower current output than the rating 2.5 A

As try fixing SMPS having improper lower current output than the rating 2.5 A 24V, encountered that the SMPS gives output 24 V if Q is used in normal i.e. jumper is closed, but 35 V if it opens, all without sufficient current/power produced as the claimed rated one



Any clear make-sense reasoning why it is so, and what is the culprit that fails having the proper, adequate current/power, so that can troubleshoot and fix the best way?