Thanks for posting! To your question we have in fact heard of this before. In some cases the cause is the gas lift mechanism in some chairs generating an electromagnetic interference (EMI) spike that causes the issue. DisplayLink, the maker of the chip in our dock, speaks to this issue in their knowledge-base here:
A customer also posted his experience with this type of behavior with a similar Dell docking station here:
He was even able to capture the behavior on video. In his case swapping the chair with a different one solved the problem.
There is even more detail in this DisplayLink forum thread about the behavior:
Please let us know if that information helps!