I bought a Rocktron Hypnotic Flanger off of eBay. It worked fine for about a week, but now it is completely messed up. Basically when I'm not playing guitar there is a sound like a heartbeat, and when I am playing the guitar the effect cuts in and out with the heartbeat. Oddly enough the knobs now control the heartbeat/cutting in and out, for example the rate knob controls the speed of the heartbeat, the depth knob controls the intensity of the heartbeat, etc. Certain adjustments of the various knobs can stop the heartbeat/cutting in and out, but these are adjustments that leave little to no effect, for example rate turned all the way down, depth turned most of the way down depending on how low the rate is, manual turned a certain amount up, etc.

If anyone has advice or has experience similar problems with their flanger or other pedals, please don't hesitate to reply. Thank you very much.
I had it hooked up to my one spot, and I tried new batteries, but that doesn't help. Thanks anyway
Put a battery in there. Plug it into your amp and guitar. Open it up and tap different parts with a chopstick or insulated screw driver. It sounds like a leaky cap or a cap is shorting to a different part of the circuit. If you tap something and the sound gets right, that component needs it solder joint to be resoldered.