Periodic thud sound washing towels and never happens with clothes

Washer Repair
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1

Brand: LG
Model Number: WM4200HBA
Main Symptom: Periodic thud only with towels (sometimes)
What happens & when:

We have a somewhat newer LG WM4200HBA washer. Recently we noticed that on occasion only with towels it will sometimes make a periodic thud sound… this never happens with clothes. I am trying to figure out what parts might be failed that could be causing this not always but periodic thud and only with some loads of towels only.

Thoughts on what could be causing the periodic thud and what to investigate?

2

Normally, when there is a thud only when washing certain things, it sounds like the unit may be getting off balance just a little and the tub bangs against the cabinet. This is the most common cause for this not a failed part.