Have Mercedes Questions? Ask a Mechanic for Answers ASAP
Did you happen to lock at the wiring pins of the connector for the latch. It is very common for corrosion to cause all sorts of weird problems with that latch. Water gets in though the rear wiper seal or through the chrome trim piece that goes around the trunk lid handle. Sometimes the handle wiring connector can get corrosion in there as well so I would suggest opening it back up and inspecting for any corrosion. If there is no corrosion, then yes, a shorted tailgate handle can cause this problem.
Let me know if you need any more help, thanks!