False positive from a non-contact voltage tester?
Trust the multimeter. No-contact testers should only be used for a preliminary test. If the no-contact indicates power a regular voltage tester or DMM should be used to verify.

A no-contact tester is susceptible to induced currents from wiring running in the same conduit or in close proximity to the wiring being tested.

Safety first though. Make sure circuits are de-energized before working in them.