You described a power gear system. Some noise is normal.. If it's every 3 seconds I'd try lubing the tooths on the toothed rail to see if that makes a differnce. Sounds like one of the gears may have a not so smooth spot.
This will cause a problem in oh, about 50 years or so.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times