I Agree with Ingvar, maybe the supply line is unsufficient. Can you try.. if available LVP.

trying another PC can be also a solution, but try adding Buffer/driver(lets say opamp or voltage comparator) on DBs pins

that's really weird... is your supply line neat, without any noise, can 0.1uf ceramic and 10uF tantalum(47uF electrolytic) be add-on.