This is a fairly common thing on mid-range sets. (Not the $130 paperweights, but also not quite a $299 "quality" set, using a 27" tabletop circa 2005 for pricing reference..)
There's a feature they came up with where the horizontal sweep ramp is varied so that it runs slower over high intensity elements and speeds the hell up over dark or black areas. This is combined with some "clever" electron gun modulation and results in a seemingly sharper picture with better contrast, but when certain patterns are displayed, resonance points in the H-yoke do some weird things.
This usually shows up on scenes that aren't composed of "normal" items. So a mountain vista is just fine, but if you're looking at something with lots of vertical elements things go a bit wobbly. Text is a big thing there. I know Toshiba specifically designed their sets around that problem when displaying closed captions by disabling the fancypants circuit when the beam entered the CC draw area. Most others didn't care and left it on, or just altered the font a bit...
Back in 2006 I could have told you which manufacturers (ab)used this technique specifically, but detailed knowledge like that has little use outside of retail CE sales, and I repurposed that bunch of brain-cells about 3 years after I took a running jump off the deck of that sinking ship...
Edit: I lubricated some of those brain cells and managed to extract the following from them after some careful forensic analysis:
The feature I refer to above is "officially" known as: Scan Velocity Modulation, but may go by other unremembered names depending on the manufacturer... Turn it off, if its not in the user menu, get the codes to access the service menu (Be careful, only change things that you know what they do, it is possible to change things such that you can't see the menu to fix them.) and disable it there.
Basically it was a flashy feature that made them appear better on display in the store, but turned out to be terrible in your own home.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvv: Forget everything I said. I don't think they had SVM in 1985, or if they did it wasn't over-used. Is the plug polarized? If not try flipping it over.