Need a 2nd opinion on a monitor problemo

Got a Dell-badged 17" sony Trinitron here, it was refurbed about 2 years ago, and dates from about 1998. It's a damn nice screen, and I like it a lot, however, it's developed a problem.

Every now and then, the image starts "shadowing" as one or two feint impressions of the displayed image appear to the right of the true image, this can be corrected by a degauss orf 4.

It cost £100, so is no great loss if it is toast, it's had a good innings, but I'd just like a second opinion before I send it to the big shadowmask in the sky.

I'll post a pic next time it does it.

Anything magnetic around it, or anything that uses alot of juice like air conditioner or fridge?

Nope, even moved it elsewhere to verify. Looks like a slipped shadowmask to me, apart from the fact it goes back with a degauss.