That could be very sensitive to the level of signal going into it. It looks like you're really hitting it hard toward the end of your plot there. That's just not a realistic scenario. Who knows what software will do in that case. Generate a wav file that has bursts of 1KHz tones spaced 1s apart. Then play that into your circuit but adjust the level until you just start to get some compression (like 2-3dB). Then evaluate your attack / release times. Then adjust the signal so that you get 10dB of compression and evaluate again. Maybe there is no problem. If there is, check resistances with your meter between J7-1 and ground. It should be 270K when release is at it's slowest setting and only 1K or less at the fastest setting. Maybe you have the pot wires reversed? If it's not 1K-ish in the lowest setting, you have a wiring issue.
Also your schematic is far to small to be useful.